Question

I have looked all over for an answer and hope someone here can help. I have a script that runs when you check a check box from a group of checkboxes. The checkboxes are assigned a value of “customer id”

<input type="checkbox" name="inv_add[]" onclick="setcid(\''.$result['cid'].'\')" value='.$result['id'].'/>

the point of the javascript is to assign a value to a hidden field telling the next page what the customer id is for all of checked boxes.

If you the user checks a box that is assigned to a different customer (therefore does not belong in the group) i want to alert the user and then uncheck the last box checked.
I can get all the way to the alert but can not uncheck the box the user just checked.

function setcid(cid) {

if (window.set_x === undefined) {
    sethidden = document.getElementById('cid');
    sethidden.value = cid;
    set_x = cid;
    alert ("finished setting x");

    }

    else if (cid !== set_x){
            alert ("You are trying to add two different companies to the same invoice");
                           /*Uncheck the box just checked by user*/
            }

        else {
            alert("they are the same");
                           /*no modification required*/
            }

}

Answer 1

You can pass the this object as you call the function:

http://jsfiddle.net/msV24/

HTML

<input type="checkbox" name="inv_add[]" onclick="setcid(\''.$result['cid'].'\',this)" value='.$result['id'].'/>

javascript

function setcid(cid, sender) {

...

    else if (cid !== set_x){
        alert ("You are trying to add two different companies to the same invoice");
                       sender.checked = false;
        }

    else {
        alert("they are the same");
                       /*no modification required*/
        }

}