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JavaScript array map function 

Dr. Xi
Joined:
04/09/2007
Posts:
753

October 07, 2010 19:20:55    Last update: January 11, 2011 19:59:17
Like the string trim function, Firefox provides a native implementation for array map, IE doesn't. So we have to create our own map function for Array: 
if(typeof Array.prototype.map !== 'function') {
	Array.prototype.map = function(fn) {
		for (i=0, r=[], l = this.length; i < l; r.push(fn(this[i++])));
			return r;
	};
}


Test page:
  • Code
  • Demo
<html>
    <head>
        <title>Array Map</title>
    </head>

    <body>
        <script language="javascript" type="text/javascript">
	    if(typeof Array.prototype.map !== 'function') {
		Array.prototype.map = function(fn) {
		    for (i=0, r=[], l = this.length; i < l; r.push(fn(this[i++])));
		    return r;
		};
	    }

            var original = ['1', '2', '3', '4'];
            document.write('<b>Original items:</b><br>');
            document.write('======================<br>');
			for (var i = 0; i < original.length; i++) {
                document.write(original[i] + '<br>');
            }

            var mapped = original.map(function(i) {
			    return 'div' + i;
			 });
            document.write('<br><b>Mapped items</b><br>');
            document.write('======================<br>');
            for (var i = 0; i < mapped.length; i++){
                document.write(mapped[i] + '<br>');
            }
        </script>
    </body>
</html>
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