原生jQuery代码

function myJquery(selector){
    if(typeof selector=="string") {
        if (selector.charAt(0) == "<" && selector.slice(-1) == ">") {
            var ele = selector.slice(1,-1);
            this[0] = document.createElement(ele);
            this.length = 1;
        } else {
            var all=document.querySelectorAll(selector);
            for (var i = 0; i < all.length; i++) {
                this[i] = all[i];
            }
            this.length = all.length;
        }
    }else if(typeof selector=="undefined"){
        return this;
    }else if(typeof selector=="function"){
        this.ready(selector);
    }else if(selector.nodeType==1){
        this[0]=selector;
        this.length=1;
    }
}

myJquery.prototype={
    each:function(callback){
        for (var i=0;i<this.length;i++){
            callback(i,this[i]);
        }
    },
    html:function(val){
        this.each(function(index,obj){
            obj.innerHTML=val
        });
        return this;
    },
    css:function(attr,val){
        this.each(function(index,obj){
            if (typeof attr=="object"){
                for (var i in attr){
                    if (i=="width"||i=="height"||i=="margin"||i=="fontSize"){
                        obj.style[i]=parseInt(attr[i])+"px";
                    }
                    obj.style[i]=attr[i];
                }
            }else{
                obj.style[attr]=val;
            }
        })
        return this;
    },
    ready:function(callback){
        document.addEventListener("DOMContentLoaded",function(){
            callback();
        })
    },
    click:function(callback){
        this.each(function(index,obj){
            obj.onclick=function(){
                callback.call(obj);
            }
        })
        return this;
    },
    appendTo:function(dom){
        if (typeof dom=="string"){
            var all=document.querySelectorAll(dom)
            var ele=this[0]
            for (var i=0;i<all.length;i++){
                this[i]=ele.cloneNode(true)
                all[i].appendChild(this[i])
                this.length=all.length
            }
        }else{
            dom.appendChild(this[0])
        }
        // document.querySelector(dom).appendChild(this[0]);
        return this;
    }

}
function $(selector){
     return new myJquery(selector);
}