pinceladasdaweb/gist:5612973

## gistfile1.html
<!doctype html>
<html>
    <head>
        <meta charset="utf-8">
        <meta name="description" content="">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <title>Restricting File Type Before Uploading with JavaScript</title>
    </head>
    <body>
        <input type="file" name="upload" id="upload">

        <script>
  		var addEvent = (function () {
			    var setListener = function (el, ev, fn) {
			        if (el.addEventListener) {
			            el.addEventListener(ev, fn, false);
			            setListener = function (el, ev, fn) {
			                el.addEventListener(ev, fn, false);
			            };
			        } else if (el.attachEvent) {
			            el.attachEvent('on' + ev, fn);
			            setListener = function (el, ev, fn) {
			                el.attachEvent('on' + ev, fn);
			            };
			        } else {
			            el['on' + ev] =  fn;
			            setListener = function (el, ev, fn) {
			                el['on' + ev] =  fn;
			            };
			        }
			    };

			    return function (el, ev, fn) {
			        setListener(el, ev, fn);
			    };
			}());

			var upload = document.getElementById('upload');

			addEvent(upload, 'change', function(){
				if (/.*(\.jpg|\.gif|\.png)$/i.test(this.value)){
					alert('Ok, this extension is allowed');
				} else {
					alert('Please only upload files that end in types: \n\n .jpg, .gif or .png');
					this.value = '';
				}
			})
        </script>
    </body>
</html>
	<!doctype html>
	<html>
	<head>
	<meta charset="utf-8">
	<meta name="description" content="">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title>Restricting File Type Before Uploading with JavaScript</title>
	</head>
	<body>
	<input type="file" name="upload" id="upload">

	<script>
	var addEvent = (function () {
	var setListener = function (el, ev, fn) {
	if (el.addEventListener) {
	el.addEventListener(ev, fn, false);
	setListener = function (el, ev, fn) {
	el.addEventListener(ev, fn, false);
	};
	} else if (el.attachEvent) {
	el.attachEvent('on' + ev, fn);
	setListener = function (el, ev, fn) {
	el.attachEvent('on' + ev, fn);
	};
	} else {
	el['on' + ev] = fn;
	setListener = function (el, ev, fn) {
	el['on' + ev] = fn;
	};
	}
	};

	return function (el, ev, fn) {
	setListener(el, ev, fn);
	};
	}());

	var upload = document.getElementById('upload');

	addEvent(upload, 'change', function(){
	if (/.*(\.jpg\|\.gif\|\.png)$/i.test(this.value)){
	alert('Ok, this extension is allowed');
	} else {
	alert('Please only upload files that end in types: \n\n .jpg, .gif or .png');
	this.value = '';
	}
	})
	</script>
	</body>
	</html>