update String#trim

Check for two commonly erroneously trimmed characters instead of one, and check for erroneously failing to trim the trimmable whitespace characters; then use `aa*` instead of `a+`, and two regexes instead of one, both because they are more performant (it is also more performant to first trim from the beginning and then trim from the end).

I would also replace `if (typeof this === 'undefined' || this === null)` with `if (this == null)` but I don't know whether that's allowed by this library's style rules.

Author: lewisje

es6-shim.js

@@ -644,23 +644,22 @@
     overrideNative(String.prototype, 'includes', StringPrototypeShims.includes);
   }
 
-  var hasStringTrimBug = '\u0085'.trim().length !== 1;
+  // whitespace from: http://es5.github.io/#x15.5.4.20
+  // implementation from https://github.com/es-shims/es5-shim/blob/v3.4.0/es5-shim.js#L1304-L1324
+  var ws = '\x09\x0A\x0B\x0C\x0D\x20\xA0\u1680\u180E\u2000\u2001\u2002\u2003\u2004' +
+    '\u2005\u2006\u2007\u2008\u2009\u200A\u2028\u2029\u202F\u205F\u3000\uFEFF';
+  var hasStringTrimBug = ws.trim() || '\u0085\u002B'.trim().length !== 2;
   if (hasStringTrimBug) {
     delete String.prototype.trim;
-    // whitespace from: http://es5.github.io/#x15.5.4.20
-    // implementation from https://github.com/es-shims/es5-shim/blob/v3.4.0/es5-shim.js#L1304-L1324
-    var ws = [
-      '\x09\x0A\x0B\x0C\x0D\x20\xA0\u1680\u180E\u2000\u2001\u2002\u2003',
-      '\u2004\u2005\u2006\u2007\u2008\u2009\u200A\u202F\u205F\u3000\u2028',
-      '\u2029\uFEFF'
-    ].join('');
-    var trimRegexp = new RegExp('(^[' + ws + ']+)|([' + ws + ']+$)', 'g');
+    var wsRegexpChars = '[' + ws + '][' + ws + ']*';
+    var trimBeginRegexp = new RegExp('^' + wsRegexChars);
+    var trimEndRegexp = new RegExp(wsRegexChars + '$');
     defineProperties(String.prototype, {
       trim: function trim() {
         if (typeof this === 'undefined' || this === null) {
           throw new TypeError("can't convert " + this + ' to object');
         }
-        return String(this).replace(trimRegexp, '');
+        return String(this).replace(trimBeginRegexp, '').replace(trimEndRegexp, '');
       }
     });
   }