Question

I apologize in advance for such a basic question, but searching Google keeps returning largely irrelevant answers.

I want to make a web form that does realtime math. That simple. For example I type 5 into a box and immediately 20 appears in a box below it. This is because it is multiplying it by 4 on the fly. I erase the 5 and replace with a 20 and boom, there’s an 80.

I believe that after I have this building block I can do two things: Make a real time price sheet (i.e.. Apple Online Store click a box and the price changes in real time) and do automatic contract math for us personally.

Answer 1

First, you’ll need to name the text box like so:

Math:<input type="text" id="MathTB"/>

Here’s the reference website for the jQuery "Keyup" function

and the ID selector

var mathTextBox = $("#MathTB");  
mathTextBox.keyup(function () {
    var value = mathtextbox.val();
    value *= 4;
    mathTextBox.val(value);
});

Using jquery, this should get you where you’re trying to go.

Please continue to use that site as a first resource, and you will be an expert in no time.