jQuery TrapKey plugin

Description

This plugin is used for trapping the event of key press, especially useful in jQuery online game design.

Demonstration

Detecting Special Key (Press arrows or ctrl):

<p>Detecting Special Key (Press arrows or ctrl):<span id="result"></span></p>
<script type="text/javascript" src="/js/jquery.js"></script>
<script type="text/javascript" src="/js/jquery.trapkey.js"></script>
<script type="text/javascript">
(function($){
	$("document").ready(function(){
		$.trapKey("UP").setEvent(function(){
			$("#result").text("↑");
		});
		$.trapKey("DOWN").setEvent(function(){
			$("#result").text("↓");
		});
		$.trapKey("LEFT").setEvent(function(){
			$("#result").text("←");
		});
		$.trapKey("RIGHT").setEvent(function(){
			$("#result").text("→");
		});
		$.trapKey("CTRL").setEvent(function(){
			$("#result").text("Ctrl");
		});
	});
})(jQuery);
</script>

jQuery Plugin Source Code

The following is the source code of the jQuery Plugin.

<script type="text/javascript">
(function($){
	var Kb_keys=new Array(),
		Kb_lastkey=-1,
		Kb_keystrapped=0,
		Kb_lastcode=-1;
	$.trapKey=function(akey){
		return (new TrappedKey(akey.toUpperCase()));
	};
	$.clearAllTrapedKey=function(akey){
		var n;
		for(n in Kb_keys)Kb_keys[n]=null
	};
	function kp(wch,state){
		if(Kb_keys[wch]){
			Kb_keys[wch].pressed=state;
			Kb_lastkey=Kb_keys[wch];
			if(state&&Kb_keys[wch].event){
				Kb_keys[wch].event()
			}else return false;
		}
	}
	function TrappedKey(newkey){
		if(Kb_keystrapped==0){
			if(window.event){
				document.body.onkeydown=function(){
					Kb_lastcode=window.event.keyCode;
					kp(window.event.keyCode,true)
				};
				document.body.onkeyup=function(){
					kp(window.event.keyCode,false)
				};
			}else {
				document.onkeydown=function(evt){
					Kb_lastcode=evt.which;
					kp(evt.which,true)
				};
				document.onkeyup=function(evt){
					kp(evt.which,false)
				};
			} 
		}
		if(newkey.length>1){
			var c=0;
			switch(newkey){
				case 'SHIFT':
				c=16;break;
				case 'CTRL':
				c=17;break;
				case 'UP':
				c=38;break;
				case 'DOWN':
				c=40;break;
				case 'INSERT':
				c=45;break;
				case 'LEFT':
				c=37;break;
				case 'RIGHT':
				c=39;break;
				case 'ESC':
				c=27;break;
				default:
				c=0
			}
			this.code=c;
		}else
			this.code=newkey.charCodeAt(0);
		this.pressed=false;
		this.event=null;
		Kb_keys[this.code]=this;
		if(newkey.length==1&&newkey.toUpperCase()!=newkey.toLowerCase()){
			this.code=newkey.toLowerCase().charCodeAt(0);
			Kb_keys[this.code]=this;
		}
		Kb_keystrapped++;
		return this;
	}
	TrappedKey.prototype.setEvent=function(x){
		this.event=x;
		return this
	};
	TrappedKey.prototype.clearEvent=function(x){
		this.event=null;
		return this
	};
})(jQuery);</script>

Download the plugin

Click the link for downloading the plugin.

Copyright and licensing

All the plugin source codes and the examples are copyright of C. F., Wong
Please feel free to use any code listed in this page, they are licensed under the MIT License:
http://www.opensource.org/licenses/mit-license.php