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

src/string.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 872 matching lines @@
 
 
 // Helper function for very basic XSS protection.
 function HtmlEscape(str) {
   return TO_STRING_INLINE(str).replace(/</g, "&lt;")
                               .replace(/>/g, "&gt;")
                               .replace(/"/g, "&quot;")
                               .replace(/'/g, "&#039;");
 }
 
+// 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.
 function StringLink(s) {
   return "<a href=\"" + HtmlEscape(s) + "\">" + this + "</a>";
 }
 
 
 function StringAnchor(name) {
   return "<a name=\"" + HtmlEscape(name) + "\">" + this + "</a>";
@@ skipping 100 matching lines @@
     "fontcolor", StringFontcolor,
     "fontsize", StringFontsize,
     "big", StringBig,
     "blink", StringBlink,
     "bold", StringBold,
     "fixed", StringFixed,
     "italics", StringItalics,
     "small", StringSmall,
     "strike", StringStrike,
     "sub", StringSub,
-    "sup", StringSup
+    "sup", StringSup,
+    "endsWith", StringEndsWith
   ));
 }
 
 SetUpString();