Page 158 - JavaScript

Chapter 15: Bitwise Operators - Real World

Examples (snippets)

Examples

Number's Parity Detection with Bitwise AND

Instead of this (unfortunately too often seen in the real code) "masterpiece":

function isEven(n) {
return n % 2 == 0;
}

function isOdd(n) {
if (isEven(n)) {
return false;
} else {
return true;
}
}

You can do the parity check much more effective and simple:

if(n & 1) {
console.log("ODD!");
} else {
console.log("EVEN!");
}

(this is actually valid not only for JavaScript)

Swapping Two Integers with Bitwise XOR (without additional memory
allocation)

var a = 11, b = 22;
a = a ^ b;
b = a ^ b;
a = a ^ b;
console.log("a = " + a + "; b = " + b);// a is now 22 and b is now 11

Faster multiplication or division by powers of 2

Shifting bits left (right) is equivalent to multiplying (dividing) by 2. It's the same in base 10: if we
"left-shift" 13 by 2 places, we get 1300, or 13 * (10 ** 2). And if we take 12345 and "right-shift" by 3
places and then remove the decimal part, we get 12, or Math.floor(12345 / (10 ** 3)). So if we
want to multiply a variable by 2 ** n, we can just left-shift by n bits.

https://riptutorial.com/ 115