JS document.all function usage example_Basic knowledge

1.
document.all is a collection of all elements in the page. For example:
document.all(0) represents the first element in the page
2.
document.all can determine whether the browser is IE
if(document.all){
alert ("is IE!");
}
3.
You can also set the id attribute (id=aaaa) to an element, and then call the element with document.all.aaaa
4 .
Case:

Code 1:

Copy code The code is as follows:

Code 2:
But often name It can be the same (for example: using checkbox to get multiple hobbies of the user)

Copy code The code is as follows:

Code 3:
Theoretically, the ids in a page are different from each other. If If different tags have the same id
document.all.id, it will fail, like this:

Copy code Code As follows:

Code 4:
For a complex page (the code is very long, or The id is automatically generated by the program), or if it is a program written by a JavaScript beginner, it is very likely that two tags will have the same id.
In order to avoid errors when programming, I recommend writing like this:

Copy the code The code is as follows: