Deep Dive: JavaScript Inner Functions...

[SlightlyLoony]

Here's a simple and very useful feature of JavaScript that you may not be aware of: functions may be nested, one inside another. Here's a simple example, in a script you can run on your instance:

<div>
gs.log('Hex value of 11259375 is: ' + hex(11259375));

function hex(value) {
    var rem = value;
    var result = '';
    while (rem > 0) {
        var r = rem % 16;
        rem = Math.floor(rem/16);
        result = hexChar(r) + result;
    }
    return result;
   
    function hexChar(charValue) {
        return '0123456789ABCDEF'.charAt(charValue & 0xFF);
    }
}</div>

Note that the function hexChar is entirely within the function hex.

You might say: "Ok, but why on earth would I ever want to do this?" Fair question. There are at least two good reasons that I can think of: (1) you have some code that will be used repeatedly in the outer function, and which isn't useful outside that function, and (2) you can break up a large function into smaller, easier to understand (and maintain) pieces.