diff --git a/doc/API.md b/doc/API.md
index c100d1e..588a4fc 100644
--- a/doc/API.md
+++ b/doc/API.md
@@ -4,11 +4,21 @@
 
 ---
 
+## \$\$append
+
+- [source](../src/append/append.index.js)
+- [detail](../src/append/README.md)
+
 ## \$\$appendRotateTransform
 
 - [source](../src/appendRotateTransform/appendRotateTransform.index.js)
 - [detail](../src/appendRotateTransform/README.md)
 
+## \$\$appendTo
+
+- [source](../src/appendTo/appendTo.index.js)
+- [detail](../src/appendTo/README.md)
+
 ## \$\$appendTranslateTransform
 
 - [source](../src/appendTranslateTransform/appendTranslateTransform.index.js)
@@ -209,6 +219,16 @@
 - [source](../src/mergeTranslateTransform/mergeTranslateTransform.index.js)
 - [detail](../src/mergeTranslateTransform/README.md)
 
+## \$\$qs
+
+- [source](../src/qs/qs.index.js)
+- [detail](../src/qs/README.md)
+
+## \$\$qsa
+
+- [source](../src/qsa/qsa.index.js)
+- [detail](../src/qsa/README.md)
+
 ## \$\$removeAttrNS
 
 - [source](../src/removeAttrNS/removeAttrNS.index.js)
diff --git a/doc/API_KR.md b/doc/API_KR.md
index 12fcbef..5207a7f 100644
--- a/doc/API_KR.md
+++ b/doc/API_KR.md
@@ -6,6 +6,14 @@
 
 ---
 
+## \$\$append
+
+- [source](../src/append/append.index.js)
+- [detail](../src/append/README.md)
+
+첫 번째로 받은 엘리먼트를 두 번째로 받은 엘리먼트의 자식 엘리먼트로 추가합니다.
+`appendChild` 와 동일한 함수입니다.
+
 ## \$\$appendRotateTransform
 
 - [source](../src/appendRotateTransform/appendRotateTransform.index.js)
@@ -13,6 +21,14 @@
 
 `SVGTransform.SVG_TRANSFORM_ROTATE` 타입의 `SVGTransform` 의 `angle` 값에 입력받은 `angle`을 더합니다.
 
+## \$\$appendTo
+
+- [source](../src/appendTo/appendTo.index.js)
+- [detail](../src/appendTo/README.md)
+
+첫 번째로 받은 엘리먼트에 두 번째로 받은 엘리먼트를 자식 엘리먼트로 추가합니다.
+`appendChild` 와 동일한 함수입니다.
+
 ## \$\$appendTranslateTransform
 
 - [source](../src/appendTranslateTransform/appendTranslateTransform.index.js)
@@ -311,6 +327,20 @@ svg 엘리먼트에 가장 마지막으로 적용된 `SVGTransform` 이 `SVGTran
 해당 `SVGTransform` 을 svg 엘리먼트의 `x`, `y` 속성 (혹은 그에 준하는 속성) 에 반영합니다.
 svg 엘리먼트에 다른 `SVGTransform` 이 있는 경우 각 `SVGTransform` 을 업데이트합니다.
 
+## \$\$qs
+
+- [source](../src/qs/qs.index.js)
+- [detail](../src/qs/README.md)
+
+부모 엘리먼트에서 가장 먼저 셀렉터에 해당하는 자손 엘리먼트를 찾아 반환합니다. `querySelector` 와 동일한 함수입니다.
+
+## \$\$qsa
+
+- [source](../src/qsa/qsa.index.js)
+- [detail](../src/qsa/README.md)
+
+부모 엘리먼트에서 셀렉터에 해당하는 자손 엘리먼트 목록을 찾아 반환합니다. `querySelectorAll` 과 동일한 함수입니다.
+
 ## \$\$removeAttrNS
 
 - [source](../src/removeAttrNS/removeAttrNS.index.js)
diff --git a/package-lock.json b/package-lock.json
index 99e89ab..b2bfb87 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "fxsvg",
-  "version": "0.4.4",
+  "version": "0.4.5",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index 1345c8b..552a787 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "fxsvg",
-  "version": "0.4.4",
+  "version": "0.4.5",
   "description": "Functional SVG Handling Library",
   "type": "module",
   "main": "./src/index.js",
diff --git a/src/LiveScaleTransform2/LiveScaleTransform2.spec.js b/src/LiveScaleTransform2/LiveScaleTransform2.spec.js
index c9c9c2c..f18a125 100644
--- a/src/LiveScaleTransform2/LiveScaleTransform2.spec.js
+++ b/src/LiveScaleTransform2/LiveScaleTransform2.spec.js
@@ -6,6 +6,7 @@ import { makeRandomNumber } from "../../test/utils/makeRandomNumber.js";
 import { makeRandomNumberExcept } from "../../test/utils/makeRandomNumberExcept.js";
 import { makeRandomTransformAttributeValue } from "../../test/utils/makeRandomTransformAttributeValue.js";
 import { $$createSVGTransformScale } from "../createSVGTransformScale/createSVGTransformScale.index.js";
+import { $$getAttrNS } from "../getAttrNS/getAttrNS.index.js";
 import { $$getBaseTransformList } from "../getBaseTransformList/getBaseTransformList.index.js";
 import { $$isScaleSVGTransform } from "../isScaleSVGTransform/isScaleSVGTransform.index.js";
 import { $$LiveScaleTransform2 } from "./LiveScaleTransform2.index.js";
@@ -186,7 +187,7 @@ export default ({ describe, it }) => [
       live_scale_transform.$$merge();
 
       const [x2, y2, width2, height2] = mapL(
-        (k) => parseFloat($el.getAttributeNS(null, k)),
+        (k) => parseFloat($$getAttrNS(k)($el)),
         [x_name, y_name, width_name, height_name]
       );
       let expect_x;
diff --git a/src/LiveTranslateTransform/LiveTranslateTransform.spec.js b/src/LiveTranslateTransform/LiveTranslateTransform.spec.js
index 21fc67d..7797353 100644
--- a/src/LiveTranslateTransform/LiveTranslateTransform.spec.js
+++ b/src/LiveTranslateTransform/LiveTranslateTransform.spec.js
@@ -5,6 +5,7 @@ import { makeRandomInt } from "../../test/utils/makeRandomInt.js";
 import { makeRandomNumber } from "../../test/utils/makeRandomNumber.js";
 import { makeRandomTransformAttributeValue } from "../../test/utils/makeRandomTransformAttributeValue.js";
 import { $$createSVGTransformTranslate } from "../createSVGTransformTranslate/createSVGTransformTranslate.index.js";
+import { $$getAttrNS } from "../getAttrNS/getAttrNS.index.js";
 import { $$getBaseTransformList } from "../getBaseTransformList/getBaseTransformList.index.js";
 import { $$isTranslateSVGTransform } from "../isTranslateSVGTransform/isTranslateSVGTransform.index.js";
 import { $$LiveTranslateTransform } from "./LiveTranslateTransform.index.js";
@@ -121,7 +122,7 @@ export default ({ describe, it }) => [
       live_translate_transform.$$merge();
 
       const { numberOfItems: l2 } = $$getBaseTransformList($el);
-      const [x2, y2] = mapL((k) => parseFloat($el.getAttributeNS(null, k)), [
+      const [x2, y2] = mapL((k) => parseFloat($$getAttrNS(k)($el)), [
         x_name,
         y_name,
       ]);
diff --git a/src/append/README.md b/src/append/README.md
new file mode 100644
index 0000000..fbb2db0
--- /dev/null
+++ b/src/append/README.md
@@ -0,0 +1,19 @@
+# \$\$append
+
+- [source](./append.index.js)
+- [test](./append.spec.js)
+
+첫 번째로 받은 엘리먼트를 두 번째로 받은 엘리먼트의 자식 엘리먼트로 추가합니다.
+`appendChild` 와 동일한 함수입니다.
+
+```javascript
+const parent_el = $$el(`<g></g>`)();
+const child_el = $$el(`<circle cx="0" cy="0" r="10"></circle>`)();
+
+$$append(child_el)(parent_el);
+
+console.log(parent_el);
+// <g>
+//   <circle cx="0" cy="0" r="10"></circle>
+// </g>
+```
diff --git a/src/append/append.index.js b/src/append/append.index.js
new file mode 100644
index 0000000..bd4a946
--- /dev/null
+++ b/src/append/append.index.js
@@ -0,0 +1 @@
+export const $$append = (child) => (parent) => parent.appendChild(child);
diff --git a/src/append/append.spec.js b/src/append/append.spec.js
new file mode 100644
index 0000000..433f9f6
--- /dev/null
+++ b/src/append/append.spec.js
@@ -0,0 +1,19 @@
+import { expect } from "chai";
+import { $$el } from "../el/el.index.js";
+import { $$append } from "./append.index.js";
+
+export default ({ describe, it }) => [
+  describe(`$$append`, function () {
+    it(`The function append the element to the parent element as a child element.`, function () {
+      // given
+      const parent_el = $$el(`<g></g>`)();
+      const child_el = $$el(`<circle cx="0" cy="0" r="10"></circle>`)();
+
+      // when
+      $$append(child_el)(parent_el);
+
+      // then
+      expect(parent_el.contains(child_el)).true;
+    });
+  }),
+];
diff --git a/src/appendTo/README.md b/src/appendTo/README.md
new file mode 100644
index 0000000..8fd9b54
--- /dev/null
+++ b/src/appendTo/README.md
@@ -0,0 +1,19 @@
+# \$\$appendTo
+
+- [source](./appendTo.index.js)
+- [test](./appendTo.spec.js)
+
+첫 번째로 받은 엘리먼트에 두 번째로 받은 엘리먼트를 자식 엘리먼트로 추가합니다.
+`appendChild` 와 동일한 함수입니다.
+
+```javascript
+const parent_el = $$el(`<g></g>`)();
+const child_el = $$el(`<circle cx="0" cy="0" r="10"></circle>`)();
+
+$$appendTo(parent_el)(child_el);
+
+console.log(parent_el);
+// <g>
+//   <circle cx="0" cy="0" r="10"></circle>
+// </g>
+```
diff --git a/src/appendTo/appendTo.index.js b/src/appendTo/appendTo.index.js
new file mode 100644
index 0000000..b9c5e79
--- /dev/null
+++ b/src/appendTo/appendTo.index.js
@@ -0,0 +1,3 @@
+export const $$appendTo = (parent) => (child) => (
+  parent.appendChild(child), parent
+);
diff --git a/src/appendTo/appendTo.spec.js b/src/appendTo/appendTo.spec.js
new file mode 100644
index 0000000..7a5272c
--- /dev/null
+++ b/src/appendTo/appendTo.spec.js
@@ -0,0 +1,19 @@
+import { expect } from "chai";
+import { $$el } from "../el/el.index.js";
+import { $$appendTo } from "./appendTo.index.js";
+
+export default ({ describe, it }) => [
+  describe(`$$appendTo`, function () {
+    it(`The function append the element to the parent element as a child element.`, function () {
+      // given
+      const parent_el = $$el(`<g></g>`)();
+      const child_el = $$el(`<circle cx="0" cy="0" r="10"></circle>`)();
+
+      // when
+      $$appendTo(parent_el)(child_el);
+
+      // then
+      expect(parent_el.contains(child_el)).true;
+    });
+  }),
+];
diff --git a/src/el/el.spec.js b/src/el/el.spec.js
index 85f6d00..062bf00 100644
--- a/src/el/el.spec.js
+++ b/src/el/el.spec.js
@@ -1,5 +1,6 @@
 import { expect } from "chai";
 import { flatMapL, mapL } from "fxjs2";
+import { $$getAttrNS } from "../getAttrNS/getAttrNS.index.js";
 import { $$el } from "./el.index.js";
 
 const MOCK_STR = `<circle cx="10" cy="20" r="30"></circle>`;
@@ -12,9 +13,9 @@ const setupSVGList = () => [
 const expectElFromMockStr = ($el) => {
   expect($el).instanceof(SVGElement);
   expect($el.nodeName.toLowerCase()).equal("circle");
-  expect($el.getAttributeNS(null, "cx")).equal("10");
-  expect($el.getAttributeNS(null, "cy")).equal("20");
-  expect($el.getAttributeNS(null, "r")).equal("30");
+  expect($$getAttrNS("cx")($el)).equal("10");
+  expect($$getAttrNS("cy")($el)).equal("20");
+  expect($$getAttrNS("r")($el)).equal("30");
 };
 
 export default ({ describe, it }) => [
diff --git a/src/els/els.spec.js b/src/els/els.spec.js
index 9521f56..73d39db 100644
--- a/src/els/els.spec.js
+++ b/src/els/els.spec.js
@@ -11,6 +11,7 @@ import {
   zip,
 } from "fxjs2";
 import { makeRandomInt } from "../../test/utils/makeRandomInt.js";
+import { $$getAttrNS } from "../getAttrNS/getAttrNS.index.js";
 import { $$els } from "./els.index.js";
 
 const setupSVGList = () => [
@@ -79,7 +80,7 @@ export default ({ describe, it }) => [
           expect($el).instanceof(SVGElement);
           expect($el.nodeName.toLowerCase()).equal(name);
           for (const [key, expect_value] of entriesL(attrs)) {
-            const receive_value = $el.getAttributeNS(null, key);
+            const receive_value = $$getAttrNS(key)($el);
             expect(receive_value).equal(expect_value);
           }
         }
diff --git a/src/fxsvg.js b/src/fxsvg.js
index 3fe65a4..951ccff 100644
--- a/src/fxsvg.js
+++ b/src/fxsvg.js
@@ -1,4 +1,6 @@
+import { $$append } from "./append/append.index.js";
 import { $$appendRotateTransform } from "./appendRotateTransform/appendRotateTransform.index.js";
+import { $$appendTo } from "./appendTo/appendTo.index.js";
 import { $$appendTranslateTransform } from "./appendTranslateTransform/appendTranslateTransform.index.js";
 import { $$consolidateTransformList } from "./consolidateTransformList/consolidateTransformList.index.js";
 import { $$createSVGMatrix } from "./createSVGMatrix/createSVGMatrix.index.js";
@@ -38,6 +40,8 @@ import { $$mergeRotateTransform } from "./mergeRotateTransform/mergeRotateTransf
 import { $$mergeScaleTransform } from "./mergeScaleTransform/mergeScaleTransform.index.js";
 import { $$mergeScaleTransform2 } from "./mergeScaleTransform2/mergeScaleTransform2.index.js";
 import { $$mergeTranslateTransform } from "./mergeTranslateTransform/mergeTranslateTransform.index.js";
+import { $$qs } from "./qs/qs.index.js";
+import { $$qsa } from "./qsa/qsa.index.js";
 import { $$removeAttrNS } from "./removeAttrNS/removeAttrNS.index.js";
 import { $$setAttrNS } from "./setAttrNS/setAttrNS.index.js";
 import { $$updateMatrixTransform } from "./updateMatrixTransform/updateMatrixTransform.index.js";
@@ -46,7 +50,9 @@ import { $$updateScaleTransform } from "./updateScaleTransform/updateScaleTransf
 import { $$updateTranslateTransform } from "./updateTranslateTransform/updateTranslateTransform.index.js";
 
 export const FxSVG = {
+  append: $$append,
   appendRotateTransform: $$appendRotateTransform,
+  appendTo: $$appendTo,
   appendTranslateTransform: $$appendTranslateTransform,
   consolidateTransformList: $$consolidateTransformList,
   createSVGMatrix: $$createSVGMatrix,
@@ -87,6 +93,8 @@ export const FxSVG = {
   mergeScaleTransform: $$mergeScaleTransform,
   mergeScaleTransform2: $$mergeScaleTransform2,
   mergeTranslateTransform: $$mergeTranslateTransform,
+  qs: $$qs,
+  qsa: $$qsa,
   removeAttrNS: $$removeAttrNS,
   setAttrNS: $$setAttrNS,
   updateMatrixTransform: $$updateMatrixTransform,
diff --git a/src/getBoxPoints/README.md b/src/getBoxPoints/README.md
index ffc4c3f..03408d8 100644
--- a/src/getBoxPoints/README.md
+++ b/src/getBoxPoints/README.md
@@ -21,7 +21,7 @@ const str = `
 </rect>
 `;
 const $el = $$el(str)();
-$svg.appendChild($el);
+$$append($el)($svg);
 console.log($$getBoxPoints($el));
 // {original: {...}, transformed: {...}, bounding: {...}}
 // original:
diff --git a/src/getBoxPoints/getBoxPoints.spec.js b/src/getBoxPoints/getBoxPoints.spec.js
index 5535673..0093985 100644
--- a/src/getBoxPoints/getBoxPoints.spec.js
+++ b/src/getBoxPoints/getBoxPoints.spec.js
@@ -4,6 +4,7 @@ import { makeMockRect } from "../../test/utils/makeMockRect.js";
 import { makeRandomInt } from "../../test/utils/makeRandomInt.js";
 import { makeRandomNumber } from "../../test/utils/makeRandomNumber.js";
 import { makeRandomTransformAttributeValue } from "../../test/utils/makeRandomTransformAttributeValue.js";
+import { $$append } from "../append/append.index.js";
 import { $$createSVGMatrix } from "../createSVGMatrix/createSVGMatrix.index.js";
 import { $$getBaseTransformList } from "../getBaseTransformList/getBaseTransformList.index.js";
 import { $$getBoxPoints } from "./getBoxPoints.index.js";
@@ -25,7 +26,7 @@ const setupMock = ({ transform } = {}) => {
   });
 
   document.body.appendChild($svg);
-  $svg.appendChild($el);
+  $$append($el)($svg);
 
   return { x, y, width, height, $el, $svg };
 };
diff --git a/src/getCenterPoint/README.md b/src/getCenterPoint/README.md
index 306ae9e..73ec3ef 100644
--- a/src/getCenterPoint/README.md
+++ b/src/getCenterPoint/README.md
@@ -23,7 +23,7 @@ const str = `
 </rect>
 `;
 const $el = $$el(str)();
-$svg.appendChild($el);
+$$append($el)($svg);
 
 console.log($$getCenterPoint($el));
 // {original: SVGPoint, transformed: SVGPoint}
diff --git a/src/getCenterPoint/getCenterPoint.spec.js b/src/getCenterPoint/getCenterPoint.spec.js
index 4eec7be..1afc2d9 100644
--- a/src/getCenterPoint/getCenterPoint.spec.js
+++ b/src/getCenterPoint/getCenterPoint.spec.js
@@ -4,6 +4,7 @@ import { makeMockRect } from "../../test/utils/makeMockRect.js";
 import { makeRandomInt } from "../../test/utils/makeRandomInt.js";
 import { makeRandomNumber } from "../../test/utils/makeRandomNumber.js";
 import { makeRandomTransformAttributeValue } from "../../test/utils/makeRandomTransformAttributeValue.js";
+import { $$append } from "../append/append.index.js";
 import { $$createSVGPoint } from "../createSVGPoint/createSVGPoint.index.js";
 import { $$getBoxPoints } from "../getBoxPoints/getBoxPoints.index.js";
 import { $$getCenterPoint } from "./getCenterPoint.index.js";
@@ -20,7 +21,7 @@ const setupMock = ({ transform } = {}) => {
   });
 
   document.body.appendChild($svg);
-  $svg.appendChild($el);
+  $$append($el)($svg);
 
   return { $el, $svg };
 };
diff --git a/src/index.js b/src/index.js
index ada44e0..a539ca9 100644
--- a/src/index.js
+++ b/src/index.js
@@ -1,4 +1,6 @@
+export { $$append } from "./append/append.index.js";
 export { $$appendRotateTransform } from "./appendRotateTransform/appendRotateTransform.index.js";
+export { $$appendTo } from "./appendTo/appendTo.index.js";
 export { $$appendTranslateTransform } from "./appendTranslateTransform/appendTranslateTransform.index.js";
 export { $$consolidateTransformList } from "./consolidateTransformList/consolidateTransformList.index.js";
 export { $$createSVGMatrix } from "./createSVGMatrix/createSVGMatrix.index.js";
@@ -38,6 +40,8 @@ export { $$mergeRotateTransform } from "./mergeRotateTransform/mergeRotateTransf
 export { $$mergeScaleTransform } from "./mergeScaleTransform/mergeScaleTransform.index.js";
 export { $$mergeScaleTransform2 } from "./mergeScaleTransform2/mergeScaleTransform2.index.js";
 export { $$mergeTranslateTransform } from "./mergeTranslateTransform/mergeTranslateTransform.index.js";
+export { $$qs } from "./qs/qs.index.js";
+export { $$qsa } from "./qsa/qsa.index.js";
 export { $$removeAttrNS } from "./removeAttrNS/removeAttrNS.index.js";
 export { $$setAttrNS } from "./setAttrNS/setAttrNS.index.js";
 export { $$updateMatrixTransform } from "./updateMatrixTransform/updateMatrixTransform.index.js";
diff --git a/src/mergeScaleTransform2/mergeScaleTransform2.index.js b/src/mergeScaleTransform2/mergeScaleTransform2.index.js
index 8458720..c0596d5 100644
--- a/src/mergeScaleTransform2/mergeScaleTransform2.index.js
+++ b/src/mergeScaleTransform2/mergeScaleTransform2.index.js
@@ -1,6 +1,8 @@
 import { each, go, go1, mapL, rangeL, some } from "fxjs2";
+import { $$getAttrNS } from "../getAttrNS/getAttrNS.index.js";
 import { $$getBaseTransformList } from "../getBaseTransformList/getBaseTransformList.index.js";
 import { $$isValidFxScaleSVGTransformList } from "../isValidFxScaleSVGTransformList/isValidFxScaleSVGTransformList.index.js";
+import { $$setAttrNS } from "../setAttrNS/setAttrNS.index.js";
 
 const VALID_DIRECTION = new Set(["n", "ne", "e", "se", "s", "sw", "w", "nw"]);
 
@@ -29,7 +31,7 @@ export const $$mergeScaleTransform2 = ({
   );
   const [x, y, width, height] = go(
     [x_name, y_name, width_name, height_name],
-    mapL((name) => $el.getAttributeNS(null, name)),
+    mapL((name) => $$getAttrNS(name)($el)),
     mapL(parseFloat)
   );
 
@@ -57,7 +59,7 @@ export const $$mergeScaleTransform2 = ({
       [height_name, height * Math.abs(sy)],
     ],
     mapL(([k, v]) => [k, `${v}`]),
-    each(([k, v]) => $el.setAttributeNS(null, k, v))
+    each((kv) => $$setAttrNS(kv)($el))
   );
 
   each(() => transform_list.removeItem(index - 1), rangeL(3));
diff --git a/src/mergeScaleTransform2/mergeScaleTransform2.spec.js b/src/mergeScaleTransform2/mergeScaleTransform2.spec.js
index 17bc1ec..5bd2504 100644
--- a/src/mergeScaleTransform2/mergeScaleTransform2.spec.js
+++ b/src/mergeScaleTransform2/mergeScaleTransform2.spec.js
@@ -22,6 +22,7 @@ import {
   makeRandomTransformAttributeValue,
   makeMockRectInitiatedScaleTransform,
 } from "../../test/utils/index.js";
+import { $$getAttrNS } from "../getAttrNS/getAttrNS.index.js";
 import { $$getBaseTransformList } from "../getBaseTransformList/getBaseTransformList.index.js";
 import { makeInvalidCases as makeInvalidIsValidFxSVGTransformListCases } from "../isValidFxScaleSVGTransformList/isValidFxScaleSVGTransformList.spec.js";
 import { $$mergeScaleTransform2 } from "./mergeScaleTransform2.index.js";
@@ -121,7 +122,7 @@ export default ({ describe, it }) => [
 
         const [after_x, after_y, after_width, after_height] = go(
           ["x", "y", "width", "height"],
-          mapL((k) => $output.getAttributeNS(null, k)),
+          mapL((k) => $$getAttrNS(k)($output)),
           mapL(parseFloat)
         );
         const after_transform_list = deepCopyTransformList(
@@ -223,7 +224,7 @@ export default ({ describe, it }) => [
         );
         const [after_x, after_y, after_width, after_height] = go(
           ["x", "y", "width", "height"],
-          mapL((k) => $output.getAttributeNS(null, k)),
+          mapL((k) => $$getAttrNS(k)($output)),
           mapL(parseFloat)
         );
         expectNotChange(
@@ -340,7 +341,7 @@ export default ({ describe, it }) => [
 
         const [after_width, after_height] = go(
           ["width", "height"],
-          mapL((k) => $el.getAttributeNS(null, k)),
+          mapL((k) => $$getAttrNS(k)($el)),
           mapL(parseFloat)
         );
         expect(after_width).equal(before_width * Math.abs(sx));
@@ -381,7 +382,7 @@ export default ({ describe, it }) => [
           height_name: "height",
         })($el);
 
-        const after_x = parseFloat($el.getAttributeNS(null, "x"));
+        const after_x = parseFloat($$getAttrNS("x")($el));
         expect(after_x).equal(before_x);
       }
     });
@@ -419,7 +420,7 @@ export default ({ describe, it }) => [
           height_name: "height",
         })($el);
 
-        const after_y = parseFloat($el.getAttributeNS(null, "y"));
+        const after_y = parseFloat($$getAttrNS("y")($el));
         expect(after_y).equal(before_y);
       }
     });
@@ -478,7 +479,7 @@ export default ({ describe, it }) => [
           height_name: "height",
         })($el);
 
-        const after_x = parseFloat($el.getAttributeNS(null, "x"));
+        const after_x = parseFloat($$getAttrNS("x")($el));
         expect(after_x).equal((before_x - cx) * sx + cx);
       }
     });
@@ -537,7 +538,7 @@ export default ({ describe, it }) => [
           height_name: "height",
         })($el);
 
-        const after_y = parseFloat($el.getAttributeNS(null, "y"));
+        const after_y = parseFloat($$getAttrNS("y")($el));
         expect(after_y).equal((before_y - cy) * sy + cy);
       }
     });
@@ -578,7 +579,7 @@ export default ({ describe, it }) => [
           height_name: "height",
         })($el);
 
-        const after_x = parseFloat($el.getAttributeNS(null, "x"));
+        const after_x = parseFloat($$getAttrNS("x")($el));
         expect(after_x).equal((before_x - cx) * sx + cx + width * sx);
       }
     });
@@ -619,7 +620,7 @@ export default ({ describe, it }) => [
           height_name: "height",
         })($el);
 
-        const after_y = parseFloat($el.getAttributeNS(null, "y"));
+        const after_y = parseFloat($$getAttrNS("y")($el));
         expect(after_y).equal((before_y - cy) * sy + cy + height * sy);
       }
     });
diff --git a/src/mergeTranslateTransform/mergeTranslateTransform.index.js b/src/mergeTranslateTransform/mergeTranslateTransform.index.js
index c401861..08e97e0 100644
--- a/src/mergeTranslateTransform/mergeTranslateTransform.index.js
+++ b/src/mergeTranslateTransform/mergeTranslateTransform.index.js
@@ -1,8 +1,10 @@
 import { each, go, mapL, rangeL } from "fxjs2";
 import { $$createSVGTransformTranslate } from "../createSVGTransformTranslate/createSVGTransformTranslate.index.js";
+import { $$getAttrNS } from "../getAttrNS/getAttrNS.index.js";
 import { $$getBaseTransformList } from "../getBaseTransformList/getBaseTransformList.index.js";
 import { $$getSVG } from "../getSetSVG/getSetSVG.index.js";
 import { $$isTranslateSVGTransform } from "../isTranslateSVGTransform/isTranslateSVGTransform.index.js";
+import { $$setAttrNS } from "../setAttrNS/setAttrNS.index.js";
 
 export const $$mergeTranslateTransform = ({
   index = 0,
@@ -26,11 +28,11 @@ export const $$mergeTranslateTransform = ({
       { name: x_name, value: tx },
       { name: y_name, value: ty },
     ],
-    mapL(({ name, value }) => ({
+    mapL(({ name, value }) => [
       name,
-      value: `${parseFloat($el.getAttributeNS(null, name)) + value}`,
-    })),
-    each(({ name, value }) => $el.setAttributeNS(null, name, value))
+      `${parseFloat($$getAttrNS(name)($el)) + value}`,
+    ]),
+    each((kv) => $$setAttrNS(kv)($el))
   );
 
   base_transform_list.removeItem(index);
diff --git a/src/mergeTranslateTransform/mergeTranslateTransform.spec.js b/src/mergeTranslateTransform/mergeTranslateTransform.spec.js
index 862d910..a7c997a 100644
--- a/src/mergeTranslateTransform/mergeTranslateTransform.spec.js
+++ b/src/mergeTranslateTransform/mergeTranslateTransform.spec.js
@@ -14,6 +14,7 @@ import { $$createSVGTransformMatrix } from "../createSVGTransformMatrix/createSV
 import { $$createSVGTransformRotate } from "../createSVGTransformRotate/createSVGTransformRotate.index.js";
 import { $$createSVGTransformScale } from "../createSVGTransformScale/createSVGTransformScale.index.js";
 import { $$createSVGTransformTranslate } from "../createSVGTransformTranslate/createSVGTransformTranslate.index.js";
+import { $$getAttrNS } from "../getAttrNS/getAttrNS.index.js";
 import { $$getBaseTransformList } from "../getBaseTransformList/getBaseTransformList.index.js";
 import { $$mergeTranslateTransform } from "./mergeTranslateTransform.index.js";
 
@@ -46,10 +47,10 @@ export default ({ describe, it }) => [
         const { numberOfItems: transform_list_length } = $$getBaseTransformList(
           $input
         );
-        const [before_x, before_y] = mapL(
-          (k) => $input.getAttributeNS(null, k),
-          ["x", "y"]
-        );
+        const [before_x, before_y] = mapL((k) => $$getAttrNS(k)($input), [
+          "x",
+          "y",
+        ]);
         const before_transform_list = deepCopyTransformList(
           $$getBaseTransformList($input)
         );
@@ -63,10 +64,10 @@ export default ({ describe, it }) => [
           y_name: "y",
         })($input, $svg);
 
-        const [after_x, after_y] = mapL(
-          (k) => $output.getAttributeNS(null, k),
-          ["x", "y"]
-        );
+        const [after_x, after_y] = mapL((k) => $$getAttrNS(k)($output), [
+          "x",
+          "y",
+        ]);
         const after_transform_list = deepCopyTransformList(
           $$getBaseTransformList($output)
         );
@@ -99,10 +100,10 @@ export default ({ describe, it }) => [
             })(),
             index
           );
-          const [before_x, before_y] = mapL(
-            (k) => $input.getAttributeNS(null, k),
-            ["x", "y"]
-          );
+          const [before_x, before_y] = mapL((k) => $$getAttrNS(k)($input), [
+            "x",
+            "y",
+          ]);
           const before_transform_list = deepCopyTransformList(
             $$getBaseTransformList($input)
           );
@@ -113,10 +114,10 @@ export default ({ describe, it }) => [
             y_name: "y",
           })($input, $svg);
 
-          const [after_x, after_y] = mapL(
-            (k) => $output.getAttributeNS(null, k),
-            ["x", "y"]
-          );
+          const [after_x, after_y] = mapL((k) => $$getAttrNS(k)($output), [
+            "x",
+            "y",
+          ]);
           const after_transform_list = deepCopyTransformList(
             $$getBaseTransformList($output)
           );
@@ -149,10 +150,10 @@ export default ({ describe, it }) => [
             })(),
             index
           );
-          const [before_x, before_y] = mapL(
-            (k) => $input.getAttributeNS(null, k),
-            ["x", "y"]
-          );
+          const [before_x, before_y] = mapL((k) => $$getAttrNS(k)($input), [
+            "x",
+            "y",
+          ]);
           const before_transform_list = deepCopyTransformList(
             $$getBaseTransformList($input)
           );
@@ -163,10 +164,10 @@ export default ({ describe, it }) => [
             y_name: "y",
           })($input, $svg);
 
-          const [after_x, after_y] = mapL(
-            (k) => $output.getAttributeNS(null, k),
-            ["x", "y"]
-          );
+          const [after_x, after_y] = mapL((k) => $$getAttrNS(k)($output), [
+            "x",
+            "y",
+          ]);
           const after_transform_list = deepCopyTransformList(
             $$getBaseTransformList($output)
           );
@@ -198,10 +199,10 @@ export default ({ describe, it }) => [
             })(),
             index
           );
-          const [before_x, before_y] = mapL(
-            (k) => $input.getAttributeNS(null, k),
-            ["x", "y"]
-          );
+          const [before_x, before_y] = mapL((k) => $$getAttrNS(k)($input), [
+            "x",
+            "y",
+          ]);
           const before_transform_list = deepCopyTransformList(
             $$getBaseTransformList($input)
           );
@@ -212,10 +213,10 @@ export default ({ describe, it }) => [
             y_name: "y",
           })($input, $svg);
 
-          const [after_x, after_y] = mapL(
-            (k) => $output.getAttributeNS(null, k),
-            ["x", "y"]
-          );
+          const [after_x, after_y] = mapL((k) => $$getAttrNS(k)($output), [
+            "x",
+            "y",
+          ]);
           const after_transform_list = deepCopyTransformList(
             $$getBaseTransformList($output)
           );
@@ -292,8 +293,8 @@ export default ({ describe, it }) => [
           y_name: "y",
         })($input, $svg);
 
-        expect($output.getAttributeNS(null, "x")).equal(`${x + tx}`);
-        expect($output.getAttributeNS(null, "y")).equal(`${y + ty}`);
+        expect($$getAttrNS("x")($output)).equal(`${x + tx}`);
+        expect($$getAttrNS("y")($output)).equal(`${y + ty}`);
       }
     });
   }),
diff --git a/src/qs/README.md b/src/qs/README.md
new file mode 100644
index 0000000..ce901b3
--- /dev/null
+++ b/src/qs/README.md
@@ -0,0 +1,19 @@
+# \$\$qs
+
+- [source](./qs.index.js)
+- [test](./qs.spec.js)
+
+부모 엘리먼트에서 가장 먼저 셀렉터에 해당하는 자손 엘리먼트를 찾아 반환합니다. `querySelector` 와 동일한 함수입니다.
+
+```javascript
+const el = $$el(`
+  <g>
+    <circle cx="10" cy="10" r="20"></circle>
+    <rect x="20" y="20" width="200" height="120"></rect>
+  </g>
+`)();
+const child = $$qs("*", el);
+
+console.log(child);
+// <circle cx="10" cy="10" r="20"></circle>
+```
diff --git a/src/qs/qs.index.js b/src/qs/qs.index.js
new file mode 100644
index 0000000..9d71a3b
--- /dev/null
+++ b/src/qs/qs.index.js
@@ -0,0 +1 @@
+export const $$qs = (sel, base = document) => base.querySelector(sel);
diff --git a/src/qs/qs.spec.js b/src/qs/qs.spec.js
new file mode 100644
index 0000000..5ba34ad
--- /dev/null
+++ b/src/qs/qs.spec.js
@@ -0,0 +1,34 @@
+import { expect } from "chai";
+import { $$append } from "../append/append.index.js";
+import { $$el } from "../el/el.index.js";
+import { $$qs } from "./qs.index.js";
+
+export default ({ describe, it }) => [
+  describe(`$$qs`, function () {
+    it(`The function returns the element matched with the selector.`, function () {
+      // given
+      const g_el = $$el(`<g></g>`)();
+      const a_el = $$el(`<circle cx="10" cy="10" r="20"></circle>`)();
+      $$append(a_el)(g_el);
+
+      // when
+      const received = $$qs("circle", g_el);
+
+      // then
+      expect(received).equal(a_el);
+    });
+
+    it(`The function returns "null" when there is no matched element.`, function () {
+      // given
+      const g_el = $$el(`<g></g>`)();
+      const a_el = $$el(`<circle cx="10" cy="10" r="20"></circle>`)();
+      $$append(a_el)(g_el);
+
+      // when
+      const received = $$qs("rect", g_el);
+
+      // then
+      expect(received).null;
+    });
+  }),
+];
diff --git a/src/qsa/README.md b/src/qsa/README.md
new file mode 100644
index 0000000..e5e9723
--- /dev/null
+++ b/src/qsa/README.md
@@ -0,0 +1,19 @@
+# \$\$qsa
+
+- [source](./qsa.index.js)
+- [test](./qsa.spec.js)
+
+부모 엘리먼트에서 셀렉터에 해당하는 자손 엘리먼트 목록을 찾아 반환합니다. `querySelectorAll` 과 동일한 함수입니다.
+
+```javascript
+const el = $$el(`
+  <g>
+    <circle cx="10" cy="10" r="20"></circle>
+    <rect x="20" y="20" width="200" height="120"></rect>
+  </g>
+`)();
+const list = $$qsa("*", el);
+
+console.log(list);
+// NodeList(2) [circle, rect]
+```
diff --git a/src/qsa/qsa.index.js b/src/qsa/qsa.index.js
new file mode 100644
index 0000000..6aac3d4
--- /dev/null
+++ b/src/qsa/qsa.index.js
@@ -0,0 +1 @@
+export const $$qsa = (sel, base = document) => base.querySelectorAll(sel);
diff --git a/src/qsa/qsa.spec.js b/src/qsa/qsa.spec.js
new file mode 100644
index 0000000..426927c
--- /dev/null
+++ b/src/qsa/qsa.spec.js
@@ -0,0 +1,47 @@
+import { expect } from "chai";
+import { $$append } from "../append/append.index.js";
+import { $$el } from "../el/el.index.js";
+import { $$qsa } from "./qsa.index.js";
+
+export default ({ describe, it }) => [
+  describe(`$$qsa`, function () {
+    it(`The function returns a NodeList that contains elements matched with the selector.`, function () {
+      // given
+      const g_el = $$el(`<g></g>`)();
+      const class_name = "test";
+      const a_el = $$el(
+        `<circle class="${class_name}" cx="10" cy="10" r="20"></circle>`
+      )();
+      $$append(a_el)(g_el);
+      const b_el = $$el(
+        `<rect class="${class_name}" x="20" y="20" width="100" height="40"></rect>`
+      )();
+      $$append(b_el)(g_el);
+
+      // when
+      const received = $$qsa(`.${class_name}`, g_el);
+
+      // then
+      expect(received).instanceof(NodeList);
+      expect(received.length).equal(2);
+      expect(received).include(a_el);
+      expect(received).include(b_el);
+    });
+
+    it(`The function returns an empty NodeList when there is no matched elements with the selector.`, function () {
+      // given
+      const g_el = $$el(`<g></g>`)();
+      $$append($$el(`<circle cx="10" cy="10" r="20"></circle>`)())(g_el);
+      $$append($$el(`<rect x="20" y="20" width="100" height="40"></rect>`)())(
+        g_el
+      );
+
+      // when
+      const received = $$qsa(`#test`, g_el);
+
+      // then
+      expect(received).instanceof(NodeList);
+      expect(received.length).equal(0);
+    });
+  }),
+];
diff --git a/test/playground.html b/test/playground.html
index b549215..79f5315 100644
--- a/test/playground.html
+++ b/test/playground.html
@@ -26,9 +26,9 @@
 
     (() => {
       const { width, height } = document.body.getBoundingClientRect();
-      $svg.setAttributeNS(null, "width", `${width}`);
-      $svg.setAttributeNS(null, "height", `${height}`);
-      $svg.setAttributeNS(null, "viewBox", "-1000 -1000 2000 2000");
+      FxSVG.setAttrNS(["width", `${width}`])($svg);
+      FxSVG.setAttrNS(["height", `${height}`])($svg);
+      FxSVG.setAttrNS(["viewBox", "-1000 -1000 2000 2000"])($svg);
     })();
   </script>
 </html>
diff --git a/test/spec.js b/test/spec.js
index a587871..767b122 100644
--- a/test/spec.js
+++ b/test/spec.js
@@ -1,4 +1,6 @@
+import __spec_append__ from "../src/append/append.spec.js";
 import __spec_appendRotateTransform__ from "../src/appendRotateTransform/appendRotateTransform.spec.js";
+import __spec_appendTo__ from "../src/appendTo/appendTo.spec.js";
 import __spec_appendTranslateTransform__ from "../src/appendTranslateTransform/appendTranslateTransform.spec.js";
 import __spec_consolidateTransformList__ from "../src/consolidateTransformList/consolidateTransformList.spec.js";
 import __spec_createSVGMatrix__ from "../src/createSVGMatrix/createSVGMatrix.spec.js";
@@ -38,6 +40,8 @@ import __spec_mergeRotateTransform__ from "../src/mergeRotateTransform/mergeRota
 import __spec_mergeScaleTransform__ from "../src/mergeScaleTransform/mergeScaleTransform.spec.js";
 import __spec_mergeScaleTransform2__ from "../src/mergeScaleTransform2/mergeScaleTransform2.spec.js";
 import __spec_mergeTranslateTransform__ from "../src/mergeTranslateTransform/mergeTranslateTransform.spec.js";
+import __spec_qs__ from "../src/qs/qs.spec.js";
+import __spec_qsa__ from "../src/qsa/qsa.spec.js";
 import __spec_removeAttrNS__ from "../src/removeAttrNS/removeAttrNS.spec.js";
 import __spec_setAttrNS__ from "../src/setAttrNS/setAttrNS.spec.js";
 import __spec_updateMatrixTransform__ from "../src/updateMatrixTransform/updateMatrixTransform.spec.js";
@@ -47,7 +51,9 @@ import __spec_updateTranslateTransform__ from "../src/updateTranslateTransform/u
 
 export default () =>
   [
+    __spec_append__,
     __spec_appendRotateTransform__,
+    __spec_appendTo__,
     __spec_appendTranslateTransform__,
     __spec_consolidateTransformList__,
     __spec_createSVGMatrix__,
@@ -87,6 +93,8 @@ export default () =>
     __spec_mergeScaleTransform__,
     __spec_mergeScaleTransform2__,
     __spec_mergeTranslateTransform__,
+    __spec_qs__,
+    __spec_qsa__,
     __spec_removeAttrNS__,
     __spec_setAttrNS__,
     __spec_updateMatrixTransform__,
diff --git a/test/utils/makeMockRectInitializedRotateTransform.js b/test/utils/makeMockRectInitializedRotateTransform.js
index 4171553..fda4637 100644
--- a/test/utils/makeMockRectInitializedRotateTransform.js
+++ b/test/utils/makeMockRectInitializedRotateTransform.js
@@ -9,6 +9,7 @@ import {
   rangeL,
   rejectL,
 } from "fxjs2";
+import { $$getAttrNS } from "../../src/getAttrNS/getAttrNS.index.js";
 import { $$getBaseTransformList } from "../../src/getBaseTransformList/getBaseTransformList.index.js";
 import { $$initRotateTransform } from "../../src/initRotateTransform/initRotateTransform.index.js";
 import { makeMockRect } from "./makeMockRect.js";
@@ -62,7 +63,7 @@ export const makeMockRectInitializedRotateTransform = ({
   const { angle } = transform_list.getItem(index);
   const [x, y, width, height] = go(
     ["x", "y", "width", "height"],
-    mapL((name) => $el.getAttributeNS(null, name)),
+    mapL((name) => $$getAttrNS(name)($el)),
     mapL(parseFloat)
   );
 
diff --git a/test/utils/makeMockRectInitializedScaleTransform.js b/test/utils/makeMockRectInitializedScaleTransform.js
index fead7cf..a82fe9f 100644
--- a/test/utils/makeMockRectInitializedScaleTransform.js
+++ b/test/utils/makeMockRectInitializedScaleTransform.js
@@ -8,6 +8,7 @@ import {
   rangeL,
   rejectL,
 } from "fxjs2";
+import { $$getAttrNS } from "../../src/getAttrNS/getAttrNS.index.js";
 import { $$getBaseTransformList } from "../../src/getBaseTransformList/getBaseTransformList.index.js";
 import { $$initScaleTransform } from "../../src/initScaleTransform/initScaleTransform.index.js";
 import { makeMockRect } from "./makeMockRect.js";
@@ -67,7 +68,7 @@ export const makeMockRectInitiatedScaleTransform = ({
   );
   const [x, y, width, height] = go(
     ["x", "y", "width", "height"],
-    mapL((name) => $el.getAttributeNS(null, name)),
+    mapL((name) => $$getAttrNS(name)($el)),
     mapL(parseFloat)
   );
 
diff --git a/test/utils/makeMockRectInitializedTranslateTransform.js b/test/utils/makeMockRectInitializedTranslateTransform.js
index b1a7e9b..4d40088 100644
--- a/test/utils/makeMockRectInitializedTranslateTransform.js
+++ b/test/utils/makeMockRectInitializedTranslateTransform.js
@@ -8,6 +8,7 @@ import {
   rangeL,
   rejectL,
 } from "fxjs2";
+import { $$getAttrNS } from "../../src/getAttrNS/getAttrNS.index.js";
 import { $$getBaseTransformList } from "../../src/getBaseTransformList/getBaseTransformList.index.js";
 import { $$initTranslateTransform } from "../../src/initTranslateTransform/initTranslateTransform.index.js";
 import { makeMockRect } from "./makeMockRect.js";
@@ -56,7 +57,7 @@ export const makeMockRectInitializedTranslateTransform = ({
   const { e: tx, f: ty } = transform_list.getItem(index).matrix;
   const [x, y, width, height] = go(
     ["x", "y", "width", "height"],
-    mapL((name) => $el.getAttributeNS(null, name)),
+    mapL((name) => $$getAttrNS(name)($el)),
     mapL(parseFloat)
   );