Simple Captcha/Random Code Generator

/*-------------------------------------------------------- - Simple Captcha/Random Code Generator - by Uunknownn - See working at https://jsfiddle.net/uo5s12hf/ --------------------------------------------------------*/ var generateCaptcha = (function(){ // Allowed alpha/numeric characters var a = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; var n = "0123456789"; // Captcha length var cap_size = 5; // Generate a random número from 0 to X var rand = function(x){ return Math.floor(Math.random() * x); } // Build the captcha var captcha = ""; while (cap_size--) { // if 0 add a random alphabetic character if (rand(2) === 0) captcha += a[rand(a.length)]; // if 1 add a random numeric character else captcha += n[rand(n.length)]; } // Return the captcha when it's done return captcha; })(); // Print on screen document.body.innerHTML = generateCaptcha;