How make uint32 multiplications in javascript like, C makes them

Question

How make uint32 multiplications in javascript without loosing precision ?

I am trying implement C algorithm in javascript.

uint32 key = (val * 134775813) + 1;

So, all higher bytes will be lost in result.

I tried browser console:

> a1 = 591751271
591751271
> a2 = 134775813
134775813
> a4 = (a1 * a2) + 1;
79753758642808320

I made same calculation with python

Python 3.7.9 (default, Aug 18 2020, 06:22:45) 
[GCC 7.5.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> a1=591751271
>>> a2=134775813
>>> a4 = (a1 * a2) + 1
>>> print(a4)
79753758642808324

Looks similar but I am specially interested those lower bytes. Can anyone point me right direction.

I know there are built in BigInt objects, but really you cant make any operations with those.

Answer 1

Thanks to ASDFGerte . Who pointed me towards Math.imul function.

I came up with this one liner and it performed perfectly.

const uMul = (a,b) => Math.imul(a, b) >>> 0;

MDN site has polyfill function and with small change it does the same.

const uMul = (a, b) => {
  const aHi = (a >>> 16) & 0xffff;
  const aLo = a & 0xffff;
  const bHi = (b >>> 16) & 0xffff;
  const bLo = b & 0xffff;
  // the shift by 0 fixes the sign on the high part
  return (aLo * bLo) + (((aHi * bLo + aLo * bHi) << 16) >>> 0);
};