what is the meaning of the Object window['0'] and window['1'] in javascript

Question

I'am a beginners of javaScript,and i really want to know what does the Window['0'] means. I guess it may be connected with frame element of html,but how and i can not find answer in the book Professional JavaScript for Web Developers 3rd Edition.

Answer 1

https://developer.mozilla.org/en-US/docs/Web/API/Window window[0], window[1], etc. Returns a reference to the window object in the frames. See Window.frames for more details.