A JavaScript/TypeScript CRC32 implementation in only 18 lines of code.

crc32.js

// Copyright 2019 McKayla Washburn
// MIT License

// Feel free to use this however you want for whatever you want.
// Just note that the function returns a signed 32 bit number.
// This is a limitation of JavaScript's bitwise operators.
// If the value you are checking against is unsigned, then you
// can convert it to a signed 32 bit number by doing a bitshift of 0.

// Ex:
// valid >> 0 === crc32( input )

const poly = 0xEDB88320;
const lookup = new Uint32Array( 256 );
lookup.forEach( ( _, i, self ) => {
  let crc = i;
  for ( let bit = 0; bit < 8; bit++ ) {
    crc = crc & 1
      ? crc >>> 1 ^ poly
      : crc >>> 1;
  }

  self[ i ] = crc;
});

// TypeScript definition, for reference.
// export default function crc32( data: Buffer | Uint8Array | number[] ) {
export default function crc32( data ) {
  const input = Uint8Array.from( data );

  return ~input.reduce(
    ( crc, byte ) => lookup[ ( crc ^ byte ) & 0xFF ] ^ crc >>> 8,
    0xFFFFFFFF
  );
}