finding object in Javascript
Question
I have a form with thousands of checkboxes, and when one is checked, I want to check all the boxes below it. This works:
<html>
<body>
<form name="myform">
<input type="checkbox" name="box1" onClick="redrawboxes(this);">1<br>
<input type="checkbox" name="box2" onClick="redrawboxes(this);">2<br>
...
</form>
</body>
</html>
<script>
function redrawboxes(obj){
//check all boxes below
var foundit=false;
for (e=0; e<document.myform.elements.length; e++){
if (foundit==false){ //search for checked obj
if(obj == document.myform.elements[e]){
foundit=true;
}
}else{ //continuing below checked box
if(obj.checked){ //are we checking or unchecking
document.myform.elements[e].checked = true;
}else{
document.myform.elements[e].checked = false;
}
}
}
}
</script>
but for more than a few thousand boxes, IE is unacceptably slow. (Firefox works fine.) Is there a better way to find the original box besides iterating through the whole list?
5 answers
solution1
4 ACCPTED 2009-02-02 21:34:03
Both of the jQuery suggestions are pretty good. For DOM wrangling like this, you're really better off using a good library.
And the comment about the dubious wisdom of putting thousands of checkboxes on a form is pretty good as well...
But, on the off-chance that you do have a good reason for doing this, and you can't use jQuery or similar, here's a fast, straight JS method:
function redrawboxes(obj)
{
//check all boxes below
var next = obj;
while ( (next = next.nextSibling) )
{
if ( next.nodeName.toLowerCase() == "input"
&& next.type.toLowerCase() == "checkbox" )
next.checked = obj.checked;
}
}
tested in FF3, FF3.1, IE6, Chrome 1, Chromium 2
solution2
3 2009-02-02 21:09:39
i might get down voted for this, but try using jquery. it has selectors optimized for that.
solution3
2 2009-02-02 21:10:36
Advertising inside !
If you are using jQuery, you can try my plugin to make your loop asynchronous, this will allow to run a long loop without freezing the browser.
http://mess.genezys.net/jquery/jquery.async.php
If you don't want to use jQuery, you can download the plugin and modify the code for your own needs, it does not really depend on jQuery.
solution4
2 2009-02-02 21:33:12
You can read out the name of the selected checkbox like this:
function redrawboxes(obj) {
var name = obj.name;
var state = obj.checked;
// get that index
var index = name.substr(3) * 1; // just to be sure it's a number
var length = document.myform.elements.length;
var allElements = document.myform.elements
// (un)check all elements below
for (var i = index; i < length; i++) {
allElements[i].checked = state;
}
}
You could have sped up your code quite a bit by using local variables and there's an if -statement that can be replaced.
Edit: Actually that one-off-error isn't an error because that specific checkbox was (un)checked by the user himself.
solution5
2 2009-02-02 22:19:23
Dunno how fast it is, but you could try the jQuery-way, grab jQuery from www.jquery.com and insert the following code on the page:
$(function(){
$("input:checkbox").click(function(){
$(this).nextAll("input:checkbox").each(function(){
this.checked = true;
});
});
});
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