Add Array.prototype.contains

src/harmony-array.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 'use strict';
 
 // This file relies on the fact that the following declaration has been made
 // in runtime.js:
 // var $Array = global.Array;
 
@@ skipping 105 matching lines @@
   if ((end - i) > 0 && ObjectIsFrozen(array)) {
     throw MakeTypeError("array_functions_on_frozen",
                         ["Array.prototype.fill"]);
   }
 
   for (; i < end; i++)
     array[i] = value;
   return array;
 }
 
+// Proposed for ES7
+// https://github.com/domenic/Array.prototype.contains/
+// 3fb531d074eddf5d23e0a46b57ea48932e1fac69
+function ArrayContains(searchElement /*, fromIndex */) { // length == 1

[caitp (gmail), 2014/09/18 01:28:31]

arv@ has suggested using `%FunctionSetLength(function, length);` to get the
length right instead, so that we don't have tp use weirdness like %_Arguments()

[mathias, 2014/09/18 06:13:07]

Needs an extra space before `//`.

[Dmitry Lomov (no reviews), 2014/09/18 06:26:45]

Needs COERCIBLE check. (No strong preference on how you set the length of
function/access arguments)

[domenic_domenicdenicola.com, 2014/09/18 15:16:13]

There is no COERCIBLE check in the spec for any of the array methods these days.
Its presence in V8 seems to be a separate bug?

[Dmitry Lomov (no reviews), 2014/09/18 15:37:29]

Hmm, I see. Could you file a bug?

+  var O = ToObject(this);
+  var len = ToLength(O.length);
+
+  if (len === 0) {

[Dmitry Lomov (no reviews), 2014/09/18 06:26:45]

Do you need this check? The below will work just fine for zero length.

[domenic_domenicdenicola.com, 2014/09/18 15:16:13]

Yes, as otherwise we will trigger ToInteger on fromIndex, which has observable
consequences for e.g. fromIndex = { valueOf() { /* side effects */ } }

[Dmitry Lomov (no reviews), 2014/09/18 15:37:29]

Got it.

+    return false;
+  }
+
+  var n = ToInteger(%_Arguments(1));
+
+  if (n >= len) {

[Dmitry Lomov (no reviews), 2014/09/18 06:26:45]

Do you need this check? 'while' below has a check already.

[domenic_domenicdenicola.com, 2014/09/18 15:16:13]

Removed, tests still pass.

+    return false;
+  }
+
+  var k;
+  if (n >= 0) {
+    k = n;
+  } else {
+    k = len - MathAbs(n);

[Dmitry Lomov (no reviews), 2014/09/18 06:26:45]

Simply len + n?

[domenic_domenicdenicola.com, 2014/09/18 15:16:13]

Weird, I wonder why the spec used abs for indexOf (which I copied). Fixing.

+    if (k < 0) {
+      k = 0;
+    }
+  }
+
+  while (k < len) {
+    var elementK = O[k];
+    if (SameValueZero(searchElement, elementK) === true) {

[Dmitry Lomov (no reviews), 2014/09/18 06:26:45]

=== true? Why not "if (SameValueZero(...))"

[domenic_domenicdenicola.com, 2014/09/18 15:16:13]

Just going for spec-verbatimness. Will change.

+      return true;
+    }
+
+    ++k;
+  }
+
+  return false;
+}
+
 // ES6, draft 05-22-14, section 22.1.2.3
 function ArrayOf() {
   var length = %_ArgumentsLength();
   var constructor = this;
   // TODO: Implement IsConstructor (ES6 section 7.2.5)
   var array = IS_SPEC_FUNCTION(constructor) ? new constructor(length) : [];
   for (var i = 0; i < length; i++) {
     %AddElement(array, i, %_Arguments(i), NONE);
   }
   array.length = length;
   return array;
 }
 
 // -------------------------------------------------------------------
 
 function HarmonyArrayExtendArrayPrototype() {
   %CheckIsBootstrapping();
 
   // Set up non-enumerable functions on the Array object.
   InstallFunctions($Array, DONT_ENUM, $Array(
     "of", ArrayOf
   ));
 
   // Set up the non-enumerable functions on the Array prototype object.
   InstallFunctions($Array.prototype, DONT_ENUM, $Array(
+    "contains", ArrayContains,
     "find", ArrayFind,
     "findIndex", ArrayFindIndex,
     "fill", ArrayFill
   ));
 }
 
 HarmonyArrayExtendArrayPrototype();