Window.top

返回窗口层级最顶层窗口的引用。

语法

var topWindow = window.top;

window.parent 返回当前窗口的直接父对象，而 window.top 返回最顶层的窗口对象。

当你在处理父窗口的子框架（subframe），而你想获取顶层框架时，这个属性相当有用。

Specification	Status	Comment
HTML Living Standard window.top	Living Standard
HTML5 window.top	Recommendation	Initial definition

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`top`	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes Notes Full support Yes Notes Notes Starting in Firefox 6, this property is read only, as defined by the standard.	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes