Example of a bit field in javascript. Packing RGBA values into a single 32bit integer

32bitpacking.js

function logBinary(number){
  console.log((number >>> 0).toString(2).replace(/(.{8})/g, " "));
}
var startBit = 8;
var bitsToGet = 8;

var alpha = 45;
var red = 187;
var green = 255;
var blue = 56;

//         [ ALPHA ]  [ RED ]  [ GREEN ]  [ BLUE ]
//            8bit   +  8bit +   8bit  +   8bit   = 32bits
// Starts:    24th      16th     8th       0
var argb = (alpha << 24) | (red << 16) | (green << 8) | blue;
logBinary(argb);

// For unpacking a bitfield we use bitwise operations
// In this case we use a mask with a AND to strip the required bits
// (1 << x) - 1) - shifts the first "x" bits
// ((1 << x) - 1) << y  -  transverses the start of the shift "y" bits
var unpackingMask = ((1 << bitsToGet) - 1) << startBit
var unpackedBits = argb & unpackingMask;
logBinary(unpackedBits);

// Removes the tailing zeros left from the unpacking
// Shifts the bits to the start
var decimalValue = unpackedBits >> startBit

// After the last shift we are left if the required decimal number
console.log(decimalValue);

This was an incredibly helpful demonstration ty