Hi there! This is a quick doodle you can use for formatting the integer. Like, 1000 or 1000003 or other positive large integer. Integer species, mind you. Not a number with decimal point. Demo #1 For only positive integer and triggered using a click event Maximum length of 16 digits. Like, single thousand trillion. Above that, the output will ignore the last digit. Above 21 figures, lulz, it will be totally screwed up and automatically compacted using e+something . Try it out! CLICK ☺ I'm gonna format your inpoot ☺ JavaScript I use array reverse() method here because it's easier to count and append comma from the back rather than from the front. Then, after the appending, the array will be reversed back and joined. If you're new to JavaScript, here's the list of methods I use in here (you can dig more information about these from Mozilla Developers or W3Schools) : Declaring variables using var Accessing the HTML element with a unique ID u...