js 剔除數組中相同的值，合併數組中相同項

實現效果如：["2013-01","2013-02","2013-03"]

代碼如下：

var a = ["2013-01","2013-01","2013-02","2013-02","2013-02","2013-03","2013-03"];
	Array.prototype.del = function() { 
		var a = {}, c = [], l = this.length; 
		for (var i = 0; i < l; i++) { 
			var b = this[i]; 
			var d = (typeof b) + b; 
			if (a[d] === undefined) { 
				c.push(b); 
				a[d] = 1; 
			} 
		} 
		return c; 
	} 
	alert(a.del());