JavaScript - bitwise OR operator

The main goal of this article is to show how bitwise OR operation (| operator) works on the JavaScript example.

The main concept of the bitwise OR operation is to make OR operations on each corresponding bits.

Quick solution:

// ONLINE-RUNNER:browser;

const a = 3;  // 0011
const b = 5;  // 0101

const result = a | b;  // <----- bitwise OR operation example

console.log(result);                               // 7    (in dec / base 10)
console.log(result.toString(2).padStart(4, '0'));  // 0111 (in bin / base 2 )

The truth table for the OR operation is: 

So, the above table on 1 bit numbers can be presented in JavaScript as:

// ONLINE-RUNNER:browser;

console.log(0 | 0);  // 0
console.log(0 | 1);  // 1
console.log(1 | 0);  // 1
console.log(1 | 1);  // 1

More complex example

// ONLINE-RUNNER:browser;

const a = 3;  // 00000011
const b = 5;  // 00000101

const result = a | b;  // <----- bitwise OR operation example

                                  // (in dec / base 10)
console.log(a);                   // 3   
console.log(b);                   // 5
console.log(result);              // 7

                                  // (in bin / base 2 )
console.log(getBits(a, 8));       // 00000011
console.log(getBits(b, 8));       // 00000101
console.log(getBits(result, 8));  // 00000111


// Helpers:

function getBits(number, length) {
	let text = '';
  	for (let i = length - 1; i > -1; --i) {
    	text += 0x01 & (number >> i);
    }
  	return text;
}

Bitwise OR operation limitations

Hint: in JavaScript, bitwise OR works on 32-bit integers. If number is bigger, the most significant bits are dicarded to get 32-bit integer number - it means only bits indexed from 0 to 31 will be used.

So, the above table can be also written as:

    3 (base 10) = 00000000000000000000000000000011 (base 2)
    5 (base 10) = 00000000000000000000000000000101 (base 2)
                  --------------------------------
3 | 5 (base 10) = 00000000000000000000000000000001 (base 2) = 7 (base 10)

Features

1. bitwise OR operation is fast - easy to do by any CPU.

See also

1. JavaScript - bitwise operators

2. JavaScript - bitwise NOT example

3. JavaScript - bitwise AND example

4. JavaScript - bitwise XOR example

5. JavaScript - get supported max integer value

References

1. Logical disjunction (OR) - Wikipedia
2. Bitwise operation - Wikipedia