document.getElementByID() does not always work on cross browser, and sometime it returns null In this case, we can use document.getElementsByTagName() to loop through all the “input” and assign values Example: var Inputs = document.getElementsByTagName(“input”); for (var obj = 0; obj < Inputs.length; obj++){ var Obj = Inputs[obj]; try{ if (Obj.checked){ // some code, do something [...]