check checkbox if another checkbox is checked

Question

I want the checkbox with the value 2 to automatically get checked if the checkbox with the value 1 is checked. Both have the same id so I can't use getElementById.

html:

<input type="checkbox" value="1" id="user_name">1<br>
<input type="checkbox" value="2" id="user_name">2

I tired:

var chk1 = $("input[type="checkbox"][value="1"]");
var chk2 = $("input[type="checkbox"][value="2"]");

if (chk1:checked)
      chk2.checked = true;

Answer 1

You need to change your HTML and jQuery to this:

var chk1 = $("input[type='checkbox'][value='1']");
var chk2 = $("input[type='checkbox'][value='2']");

chk1.on('change', function(){
    chk2.prop('checked',this.checked);
});

1. id is unique, you should use class instead.

2. Your selector for chk1 and chk2 is wrong, concatenate it properly using ' like above.

3. Use change() function to detect when first checkbox checked or unchecked then change the checked state for second checkbox using prop().

Fiddle Demo