Adding two big numbers in javascript

Question

I've been trying to add the following numbers using javascript; 76561197960265728 + 912447736

Sadly, because of rounding in javascript it will not get the correct number, I need the number as a string.

I've tried removing the last few digits using substr and then adding the two numbers together and then putting the two strings together, sadly this doesn't work if the first of the number is a 1.

function steamid(tradelink){
    var numbers = parseInt(tradelink.split('?partner=')[1].split('&')[0]),
            base = '76561197960265728';

    var number = parseInt(base.substr(-(numbers.toString().length + 1))) + numbers;
            steamid = //put back together
}

steamid('https://steamcommunity.com/tradeoffer/new/?partner=912447736&token=qJD0Oui2');

Expected: 76561198872713464

Search for node.js big integer libraries. – Barmar May 30 '19 at 01:50 — Barmar, May 30 '19 at 01:50

Renan Souza · Accepted Answer · 2020-08-21T14:30:06.790

4

welcome to StackOverflow.

For doing operations with such big integers, you should use BigInt, it will correctly operate on integers bigger than 2ˆ53 (which is the largest size that normal Number can support on JS

const sum = BigInt(76561197960265728) + BigInt(912447736);

console.log(sum.toString());

Edit 2020: This API still not widely supported by some browsers, so you may need to have a polyfill, please check this library

edited Aug 21 '20 at 14:30

answered May 30 '19 at 01:51

Renan Souza

815
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1

Woah, this makes life so much easier, thanks a lot! I'll look into it, I thought it wouldn't be possibile because of the way javascript handles large numbers. – Vizious Developer May 30 '19 at 01:53
Not very well supported at all - pretty much exclusively Chrome (errors out in latest Safari) – Jack Bashford May 30 '19 at 01:57
you can always use polyfills: https://www.npmjs.com/package/big-integer – Renan Souza Aug 21 '20 at 14:26

Adding two big numbers in javascript

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