in 方法用来判断 某属性是否在某个对象中,返回值true、false
1 console.log("alert" in window) // true
用in方法封装绑定事件处理程序
function addEvent(elem,type,fn){ "attachEvent" in window?elem.attachEvent("on"+type,fn):elem.addEventListener(elem,event,fn) }
in 方法用来判断 某属性是否在某个对象中,返回值true、false
1 console.log("alert" in window) // true
用in方法封装绑定事件处理程序
function addEvent(elem,type,fn){ "attachEvent" in window?elem.attachEvent("on"+type,fn):elem.addEventListener(elem,event,fn) }