Pass a javascript variable value into input type hidden value

Question

I would like to assign value of product of two integer numbers into a hidden field already in the html document. I was thinking about getting the value of a javascript varia

Answer 1

if you already have that hidden input :

function product(a, b) {
   return a * b;
}
function setInputValue(input_id, val) {
    document.getElementById(input_id).setAttribute('value', val);
}

if not, you can create one, add it to the body and then set it's value :

function addInput(val) {
    var input = document.createElement('input');
    input.setAttribute('type', 'hidden');
    input.setAttribute('value', val);
    document.body.appendChild(input);
}

And then you can use(depending on the case) :

addInput(product(2, 3)); // if you want to create the input
// or
setInputValue('input_id', product(2, 3));