modify checkbox using javascript

I had declared 5 checkboxes with name and id attribute in a html:

<input type="checkbox" name="category" value="One" id=11>One<br/> 
<input type="checkbox" name="category" value="Two" id=12>Two<br/> 
<input type="checkbox" name="category" value="Three" id=13>Three<br/> 
<input type="checkbox" name="category" value="Four" id=14>Four<br/>

开发者_开发知识库After declaration, I want to run a javascript that would enable the checkbox1 using that checkbox id.

Let me know to clarify something.

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Try this for checking the checkbox:

document.getElementById(<id of first checkbox>).checked = true;

Try this for enabling the checkbox:

document.getElementById(<id of first checkbox>).disabled = false;

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try

   document.myform.box1.checked = true;

or

document.getElementById('myid').checked = true;

see an full example : http://www.rgagnon.com/jsdetails/js-0007.html

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document.getElementById('checkbox1').checked = true;

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To check a check box you can use :

document.getElementById("Checkbox_ID").checked = true;

And to uncheck a check box you can use :

document.getElementById("Checkbox_ID").checked = false;

And for more info visit this page