Compare 2 fields and change color when they do not match

Question

I have a form where I am totaling up 2 columns.  When all is said and done both totals should match, but if they don't I want to change the color of one field to red and display a message. 
Thanks,
Diane

Answer 1

You can use the following custom calculation script for a hidden text field. Just make sure that it is after the other two fields in the field calculation order:
(function () {
    // Get references to the two fields
    var f1 = getField("column1_total");
    var f2 = getField("column2_total");
    // Get the field values, as numbers
    var v1 = +f1.value;
    var v2 = +f2.value;
    // If the values don't match, set f2 text color to red, otherwise black
    if (v1 !== v2) {
        f2.textColor = color.red;
        app.alert("Column values don't match.", 3);
    } else {
        f2.textColor = color.black;
This will work if you're summing integers, but not if you're summing real numbers, which is usually the case. For example, this is what JavaScript calculates for the following two additions:
0.4 + 0.5 = 0.9
0.3 + 0.6 = 0.8999999999999999
This is due to the way floating point calculations are performed in JavaScript. In such a case, the code above will consider the two values to be different, even though they may display as the same value (e.g., 0.90) in the field. To deal with this, you can round each field value to a certain number of significant digits before you compare them, like this:
    // Get the field values, as numbers rounded to two decimal places
    var v1 = util.printf("%.2f", +f1.value);
    var v2 = util.printf("%.2f", +f2.value);
and that should take care of it.