问题
I have 2 chekboxes on a page. There are wrapped in a table cell each within their own row. Doing a document.getElementById('chk1_FEAS~1005') returns the element but document.getElementById('chk5_STG2~1005') is null. For what reasons could this be happening? (I'm testing in IE 8).
<input id="chk1_FEAS~1005" value="JobStages###StageCode~JobCode###FEAS~1005" onclick="addRemoveRow(this.value,this.checked)" style="border-width:0px;padding:1px;margin:0px;height:14px;" type="checkbox" />
<input id="chk5_STG2~1005" value="JobStages###StageCode~JobCode###STG2~1005" onclick="addRemoveRow(this.value,this.checked)" style="border-width:0px;padding:1px;margin:0px;height:14px;" type="checkbox" />
回答1:
Your Id has invalid characters:
ID and NAME tokens must begin with a letter ([A-Za-z]) and may be followed by any number of letters, digits ([0-9]), hyphens ("-"), underscores ("_"), colons (":"), and periods (".").
More information here.
回答2:
document.getElementById('hk5_STG2~1005')
should be
document.getElementById('chk5_STG2~1005')
:-)
回答3:
Looking at your sample it is a typo, the second item should be, document.getElementById('chk5_STG2~1005')
Also, I would recommend removing the ~ character as it is invalid for an id.
回答4:
For what it's worth, I have similar problems using document.getElementById on checkboxes in IE8. Try adding this tag to your head section :-
<meta http-equiv="X-UA-Compatible" content="IE=7" />
This will force IE8 into IE7 compatibility mode. It works for me as a workaround until I find-out what's really up.
来源：https://stackoverflow.com/questions/1266470/document-getelementbyid-not-working