Generate numeric array index===length when appending exactly to end o…

…f array. Allowed by the rfc, and removes an extra comparison. Other minor cleanup

jiff.js

@@ -82,7 +82,7 @@ function appendListChanges(a1, a2, path, state) {
 }
 
 function lcsToJsonPatch(a1, a2, path, state, lcsMatrix) {
-	lcs.reduce(function(state, op, i, j) {
+	return lcs.reduce(function(state, op, i, j) {
 		var last, p;
 		if (op.type == lcs.REMOVE) {
 			p = path + '/' + j;
@@ -100,21 +100,19 @@ function lcsToJsonPatch(a1, a2, path, state, lcsMatrix) {
 			}
 		} else if (op.type == lcs.ADD) {
 			// See https://tools.ietf.org/html/rfc6902#section-4.1
-			// Must use '-' to indicate appending to array
-			p = path + '/' + (j === a1.length ? '-' : j);
+			// May use either index===length *or* '-' to indicate appending to array
 			state.patch.push({
 				op: 'add',
-				path: p,
+				path: path + '/' + j,
 				value: a2[i]
 			});
 		} else {
 			appendChanges(a1[j], a2[i], path + '/' + j, state);
 		}
 
 		return state;
-	}, state, lcsMatrix);
 
-	return state;
+	}, state, lcsMatrix);
 }
 
 function appendValueChanges(a, b, path, state) {

lib/jsonPatch.js

@@ -37,12 +37,12 @@ function patch(changes, x) {
 }
 
 function patchInPlace(changes, x) {
-	if(!Array.isArray(changes) || changes.length === 0) {
+	// TODO: Consider throwing if changes is not an array
+	if(!Array.isArray(changes)) {
 		return x;
 	}
 
 	return changes.reduce(function(x, change) {
-		// TODO: Throw if unsupported or invalid op
 		var op = ops[change.op];
 		if(typeof op === 'function') {
 			x = op(x, change);

test/jiff-test.js

@@ -53,10 +53,10 @@ buster.testCase('jiff', {
 
 	'diff': {
 		'on arrays': {
-			'should generate - for path suffix when appending': function() {
+			'should generate - or length for path suffix when appending': function() {
 				var patch = jiff.diff([], [1]);
 				assert.equals(patch[0].op, 'add');
-				assert.equals(patch[0].path, '/-');
+				assert(patch[0].path === '/-' || patch[0].path === '/0');
 				assert.same(patch[0].value, 1);
 			}
 		}