var core_slice = Array.prototype.slice;var proxy = function(context,fn) {    var args, proxy;    if ( typeof fn !== 'function') {        return undefined;    }    args = core_slice.call( arguments, 2 );    proxy = function() {        return fn.apply( context, args.concat( core_slice.call( arguments ) ) );    };    return proxy;};//调用1：var show = function(){    alert(this);}proxy(document,show)();  //document//调用2：var show = function(n1,n2){    alert(n1*n2);    alert(this);}proxy(document,show,3,4)();   //12   documentproxy(document,show)(3,4);   //12   documentproxy(document,show,3)(4);   //12   document//调用3：var obj = {    show:function(n1,n2){        alert(n1*n2)        alert('obj -> show');    }};document.onclick = proxy(obj,function(){    this.show(3,4);});