JS document. all function usage example _ basic knowledge

The document. all function of JS is frequently used. The following is a detailed example of how to use it.
Document. all is a collection of all elements on the page. For example:
Document. all (0) indicates the first element in the page.
II.
Document. all can judge whether the browser is IE
If (document. all ){
Alert ("is IE! ");
}
III.
You can also set the id attribute (id = aaaa) for an element, and then use document. all. aaaa to call this element.
4.
Case:

Code 1:

The Code is as follows: