Fix Array.prototype.includes

Closes #2823 Closes #2820 ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=190108636
google · Mar 23, 2018 · 29763b4 · 29763b4
1 parent bce9c36
commit 29763b4
Show file tree

Hide file tree

Showing 3 changed files with 40 additions and 6 deletions.
diff --git a/src/com/google/javascript/jscomp/js/es6/array/includes.js b/src/com/google/javascript/jscomp/js/es6/array/includes.js
@@ -38,8 +38,13 @@ $jscomp.polyfill('Array.prototype.includes', function(orig) {
       array = /** @type {!IArrayLike} */ (String(array));
     }
     var len = array.length;
-    for (var i = opt_fromIndex || 0; i < len; i++) {
-      if (array[i] == searchElement || Object.is(array[i], searchElement)) {
+    var i = opt_fromIndex || 0;
+    if (i < 0) {
+      i = Math.max(i + len, 0);
+    }
+    for (; i < len; i++) {
+      var element = array[i];
+      if (element === searchElement || Object.is(element, searchElement)) {
         return true;
       }
     }

diff --git a/src/com/google/javascript/jscomp/resources.json b/src/com/google/javascript/jscomp/resources.json
diff --git a/test/com/google/javascript/jscomp/runtime_tests/polyfill_tests/array_includes_test.js b/test/com/google/javascript/jscomp/runtime_tests/polyfill_tests/array_includes_test.js
@@ -32,17 +32,46 @@ testSuite({
     assertTrue(arr.includes(-0));
     assertTrue(arr.includes(1));
     assertTrue(arr.includes(NaN));
-    assertTrue(arr.includes(NaN, 2));
     assertTrue(arr.includes(3));
-    assertTrue(arr.includes(3, 3));
     assertFalse(arr.includes(2));
-    assertFalse(arr.includes(NaN, 3));
+
+    assertFalse([1, NaN, 3].includes(0));
+    assertFalse([1, NaN, 3].includes(-0));
+    assertFalse([0, 1, 3].includes(NaN));
+
+    // fromIndex
+    assertTrue(arr.includes(3, 3));
     assertFalse(arr.includes(3, 4));
+    assertFalse(arr.includes(3, 5));
+    assertTrue(arr.includes(3, -1));
+    assertFalse(arr.includes(0, 1));
+    assertTrue(arr.includes(0, 0));
+    assertFalse(arr.includes(0, -1));
+    assertFalse(arr.includes(0, -3));
+    assertTrue(arr.includes(0, -4));
+    assertTrue(arr.includes(0, -5));
+
+    // null and undefined
+    // Make sure the compiler knows both null and undefined are allowed
+    // to avoid a type error.
+    arr = /** @type {!Array<null|undefined>} */ ([null]);
+    assertTrue(arr.includes(null));
+    assertFalse(arr.includes(undefined));
+
+    arr = /** @type {!Array<null|undefined>} */ ([undefined]);
+    assertTrue(arr.includes(undefined));
+    assertFalse(arr.includes(null));
+
+    // empty slot
+    arr = Array(1);
+    assertTrue(arr.includes(undefined));
 
+    // string
     arr = 'abcABC';
     assertTrue(Array.prototype.includes.call(arr, 'a'));
     assertFalse(Array.prototype.includes.call(arr, 'd'));
 
+    // ArrayLike
     arr = {length: 2, 0: 5, 1: 6, 2: 7};
     assertTrue(Array.prototype.includes.call(arr, 5));
     assertTrue(Array.prototype.includes.call(arr, 6));