ts - infer, Required, Record, NonNullable

TypeScript/22.10.13 Required, Record, NonNullable.md

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+### Required, Record, NonNullable
+
+#### Required<T>
+```ts
+interface Profile {
+    name: string
+    age: number
+    married: boolean
+}
+
+
+const someone: Required<Profile> = {
+    name: 'someone',
+    age: 30,
+    married: false
+}
+
+type R<T> = {
+    [key in keyof T]-?: T[key]
+}
+```
+
+- ```-?``` Opitonal을 ```-``` Optional을 제거하는것
+
+#### Readonly<T>
+
+```ts
+interface Profile {
+    name: string
+    age: number
+    married: boolean
+}
+
+
+const someone: R<Profile, 'married'> = {
+    name: 'someone',
+    age: 30,
+    married: false
+}
+
+type R<T> = {
+    readonly [key in keyof T]: T[key]
+    // -readonly [key in keyof T]: T[key]
+    // readonly를 제거하는것
+}
+```
+
+#### Record<T>
+
+```ts
+interface Obj {
+    [key: string]: number
+}
+const a: Obj = { a: 3, b: 5, c: 7};
+const a: Record<string, number> = { a: 3, b: 5, c: 7};
+
+type _Record<T extends keyof any, S> = {
+    [key in T]: S
+}
+// <T extends keyof any>
+// 가 붙는 이유는 객체의 키가 string, number, symbol만 와야 하기 때문에 
+```
+
+#### NonNullable
+
+```ts
+type A = string | null | undefined | boolean | number;
+type B = NonNullable<A>
+// B: string | boolean | number
+
+type _NonNullable<T> = T extends null | undefined ? never : T;
+```

TypeScript/22.10.13 infer 타입 분석.md

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+### infer 타입 분석
+
+```ts
+function zip(x: number, y: string, z: boolean): { x: number, y: string, z: boolean } {
+    return { x , y, z };
+}
+
+type Params = Parameters<typeof zip>
+// Params: [x: number, y: string, z: boolean]
+type Ret = ReturnType<typeof zip>
+// Ret: [x: number, y: string, z: boolean]
+type First = Params[0];
+// First: number
+
+type _Parameters<T extends (...args: any) => any> = T extends (...args: infer A) => any ? A: never;
+```
+
+- _Parameters의 제네릭 ```<T extends (...args: any) => any>``` 는 T를 함수로 제한하는 의미이며
+- infer A: T는 함수여야하고 그 파라미터들을 A라고 한다. 이를 뒤의 삼항연산자에서 사용할것이다 라는 의미이다.
+
+```ts
+class Profile {
+    name: string;
+    age: number;
+    gender: 'male' | 'female';
+    constructor(name: string, age: number, gender: 'male' | 'female') {
+        this.name = name;
+        this.age = age;
+        this.gender = gender;
+    }
+}
+
+const p = new Profile('test', 123, 'male');
+type P = ConstructorParameters<typeof Profile>;
+type I = InstanceType<typeof Profile>;
+```