one Document.all is a collection of all the elements in a page. Such as: Document.all (0) represents the first element in the page two Document.all can tell if the browser is IE If (document. All) { Alert (” is Internet explorer!” ); } 3. You can also do this by setting the id attribute (id=aaaa) to an element, and then calling that element with document.all.aaaa Four. Case study:

Code 1:

<input name=aaa value=aaa>
<input id=bbb value=bbb>
<script language=Jscript>
alert(document.all.aaa.value) //Take value based on name
alert(document.all.bbb.value) //Take value by id
</script>

Code 2: But often the name can be the same (e.g.

<input name=aaa value=a1>
<input name=aaa value=a2>
<input id=bbb value=bbb>
<script language=Jscript>
alert(document.all.aaa(0).value) //According to a1
alert(document.all.aaa(1).value) //According to a2
alert(document.all.bbb(0).value) //This line of code will fail
</script>

Code 3: In theory, the ids in a page are different from each other. If different tags appear, they have the same id Document.all.id will fail, like this:

<input id=aaa value=a1>
<input id=aaa value=a2>
<script language=Jscript>
alert(document.all.aaa.value) //Undefined instead of a1 or a2
</script>

Code 4: For a complex page (the code is long, or the id is automatically generated by the program), or a For programs written by javascript beginners, it is very likely that two tags will have the same id. In order not to make mistakes when programming, I recommend this:

<input id=aaa value=aaa1>
<input id=aaa value=aaa2>
<input name=bbb value=bbb>
<input name=bbb value=bbb2>
<input id=ccc value=ccc>
<input name=ddd value=ddd>

<script language=Jscript>
alert(document.all("aaa",0).value)
alert(document.all("aaa",1).value)
alert(document.all("bbb",0).value)
alert(document.all("bbb",1).value)
alert(document.all("ccc",0).value)
alert(document.all("ddd",0).value)
</script>