Implemented String.prototype.endsWith as per ES6 draft 07-15-13, section 15.5.3.23

src/string.js

Index: src/string.js
diff --git a/src/string.js b/src/string.js
index cb82c166346fc7ba5491a1e9e5d28e0e9b5a5108..8a249e36ec2f70c285c96928cd7798681e14c35b 100644
--- a/src/string.js
+++ b/src/string.js
@@ -890,6 +890,39 @@ function HtmlEscape(str) {
                               .replace(/'/g, "'");
 }
 
+// ES6 draft 07-15-13, section 15.5.3.23
+function StringEndsWith(searchString /* position */) { // length == 1

[Michael Starzinger, 2013/07/29 13:16:27]

nit: Two white-spaces before comment at end of line.

+  if (IS_NULL_OR_UNDEFINED(this) && !IS_UNDETECTABLE(this)) {
+    throw MakeTypeError("called_on_null_or_undefined",
+                        ["String.prototype.endsWith"]);
+  }
+
+  var s = TO_STRING_INLINE(this);
+  var s_len = s.length;
+  var ss = TO_STRING_INLINE(searchString);
+  var ss_len = ss.length;
+
+  if (ss_len > 0) {
+    var pos = s_len;
+    if (%_ArgumentsLength() > 1) {

[Michael Starzinger, 2013/07/29 13:16:27]

There is a missing check as to whether "position" is explicitly passed an
"undefined" value, in which case "pos" should remain s.length here.

Can we add a test-case for that?

+      var arg = ToNumber(%_Arguments(1));  // position
+      if (!NUMBER_IS_NAN(arg)) {

[Michael Starzinger, 2013/07/29 13:16:27]

In case ToNumber(position) yields NaN, then "pos" should be set to 0 IIUC.
Better use the internal ToInteger() helper here, that should do the right thing.

Can we add a test-case for that?

+        pos = TO_INTEGER(arg);
+      }
+    }
+
+    var end = $Math.min($Math.max(pos, 0), s_len);

[Michael Starzinger, 2013/07/29 13:16:27]

This calls potentially monkey-patched versions of Math.min() and Math.max(),
better directly call the MathMin() and MathMax() implementations directly.

+    var start = end - ss_len;
+    if (start < 0) {
+      return false;
+    }
+
+    return %StringLastIndexOf(s, ss, start) === end - ss_len;
+  }
+
+  return true;
+}
+
 
 // Compatibility support for KJS.
 // Tested by mozilla/js/tests/js1_5/Regress/regress-276103.js.
@@ -1010,7 +1043,8 @@ function SetUpString() {
     "small", StringSmall,
     "strike", StringStrike,
     "sub", StringSub,
-    "sup", StringSup
+    "sup", StringSup,
+    "endsWith", StringEndsWith
   ));
 }