Cursed base64 encoder.

cursed_base64.ts

// It's the fastest pure-JS base64 encoder (that doesn't account for padding though) that I've found.
// It's cursed because it takes ~2s to startup and 16MB of memory 😂

const encoder = new TextEncoder ();

const lookup = (() => {
  const alphabet = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'.split ( '' );
  const lookup = new Array ( 2 ** 24 );
  const mask1 = 0b11111100_00000000_00000000;
  const mask2 = 0b00000011_11110000_00000000;
  const mask3 = 0b00000000_00001111_11000000;
  const mask4 = 0b00000000_00000000_00111111;
  for ( let i = 0, l = lookup.length; i < l; i++ ) {
    lookup[i] = alphabet[( i & mask1 ) >> 18] + alphabet[( i & mask2 ) >> 12] + alphabet[( i & mask3 ) >> 6] + alphabet[( i & mask4 )];
  }
  return lookup;
})();

const Base64 = {
  encode: ( str: string ): string => {
    const bytes = encoder.encode ( str );
    let target = '';
    for ( let i = 0, l = bytes.length; i < l; i += 3 ) {
      target += lookup[( ( bytes[i] | 0 ) << 18 ) | ( ( bytes[i] | 1 ) << 12 ) | ( ( bytes[i] | 0 ) << 6 ) | ( bytes[i] | 0 )];
    }
    return target;
  }
};