Check/uncheck all checkboxes in a form

checkall.js

function checkAll() {
    var theForm, z = 0;
    theForm = form_1;
    for(z=0; z<theForm.length;z++){
        if(theForm[z].type == 'checkbox'){
            theForm[z].checked = true;
        }
    }
}

function uncheckAll() {
    var theForm, z = 0;
    theForm = form_1;
    for(z=0; z<theForm.length;z++){
        if(theForm[z].type == 'checkbox'){
            theForm[z].checked = false;
        }
    }
}