# 下面这几个函数里面为什么用call() 这种方式呢 function.prototype.bind = function () { var self = this, context = [].shift.call(arguments), args = [].slice.call(arguments); return function () { return self.apply( context, [].concat.call(args, [].slice.call(arguments)) ) } } var objectFactory = function () { var obj = new Object, Constructor = [].shift.call( arguments ); ...... } var hasProp = {}.hasOwnProperty; var extends = function ( child, parent ) { for(var key in parent) { if (hasProp.call( parent, key)) { ...... } } ...... }