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<!doctype html>
<meta charset=utf-8>
<title>Concat test</title>
<p>View output in console ...</p>
<script>
(function () {
  var _nativeJoin = Array.prototype.join;
	var _concatJoin = function (glue) {
		var result = '';
		for(var i = 0, l = this.length; i < l; i++) {
			result += glue + this[i];
		}
		return result;
	};
	// is firefox, chrome use concat join
	// Dirty hack
	if (navigator.userAgent.indexOf("Chrome") > -1 || navigator.userAgent.indexOf("Firefox") > -1) {
		Array.prototype.join = _concatJoin;
		Array.prototype._join = _nativeJoin;
	}
	/**/

	// Main test part

	// helper
	function randomString(length) {
		var chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz'.split('');

		if (! length) {
			length = Math.floor(Math.random() * chars.length);
		}

		var str = '';
		for (var i = 0; i < length; i++) {
			str += chars[Math.floor(Math.random() * chars.length)];
		}
		return str;
	}

	// Generate array
	var source = [];
	for (var n = 1; n <= 100000; n++) {
		source.push(randomString());
	}

	// + Version
	console.time('concat "+"');
	var str1 = '';
	for(var i = 0, l = source.length; i < l; i++) {
		str1 += source[i];
	}
	console.timeEnd('concat "+"');

	// Current Array.join()
	if (!Array.prototype._join) {
		console.log('Native join');
	} else {
		console.log('Concat join');
	}
	console.time('Current Array.join()');
	var str2 = source.join("");
	console.timeEnd('Current Array.join()');


	if (Array.prototype._join) {
		// Native Join Version
		console.time('native "join" // fallback');
		var str3 = source._join("");
		console.timeEnd('native "join" // fallback');
	} else {
		console.log('no fallback');
	}

	// Debug
	console.log(str1 == str2);
	console.log(str2 == str3);
})();
</script>