javascript常用函数集锦

本文列出一些javascript常用的方法…

判断数据类型

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var isType = function(type){
	return function(obj){
		return Object.prototype.toString.call(obj) === '[object '+type+']';
	}	
}
var isArray = isType('Array')([1,2,3]);
console.log(isArray);  //true

还可以用循环语句来实现：

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var Type = {};
for (var i =0,type;type = ['String','Array','Number'][ i++ ];) {
	(function(type){
		Type[ 'is' + type] = function(obj){
			return Object.prototype.toString.call(obj) === '[object '+type+']';
		}
	})(type)
};	
console.log(Type.isString([])); //true

懒性加载函数—添加事件

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var addEvent = function(elem,type,handler){
	if(window.addEventListener){
		addEvent = function(elem,type,handler){
			elem.addEventListener(type,handler,false);
		}
	}else if(window.attachEvent){
		addEvent = function(elem,type,handler){
			elem.attachEvent('on'+type,handler);
		}
	}
	addEvent(elem,type,handler);
};

调用例子：

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var div = document.getElementById('div');
addEvent(div,'click',function(){
	alert(1);
});
addEvent(div,'click',function(){
	alert(2);
});

分时函数

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var timeChunk = function(ary, fn, count){
	var obj,
		t;
	var len = ary.length;
	var start = function(){
		for (var i =0; i<Math.min(count || 1,ary.length);i++) {
			var obj = ary.shift();
			fn(obj);
		}
	};
			
	return function(){
		t = setInterval(function(){
			if(ary.length === 0){
				return clearInterval(t);
			}
			start();
		},200);
	};
};

调用例子： 

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var ary = [];
for (var i =1;i<=1000;i++) {
	ary.push(i);
};
var rendFriendList = timeChunk(ary,function(n){
	var div = document.createElement('div');
	div.innerHTML = n;
	document.body.appendChild(div);
},8);
rendFriendList();

单例模式—绑定一次事件（例如弹出登录框）

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var getSingle = function(fn){
	var result;
	return function(){
		return result || (result = fn.apply(this,arguments));
	}
};