JavaScript Program to Add Two Binary Strings

Last Updated : 03 Jan, 2025

Here are the various ways to add two binary strings

Using parseInt() and toString()

The parseInt() method used here first converts the strings into the decimal. Ten of these converted decimal values are added together and by using the toString() method, we convert the sum back to the desired binary representation.

Syntax

parseInt(s1,2) + parseInt(s2,2).toString(2);

JavaScript

let s1 = "101010";
let s2 = "1011";
let sum = (
    parseInt(s1, 2) +
    parseInt(s2, 2)
).toString(2);
console.log(sum);

Output

2. Using BigInt Method

The approach uses the BigInt method where the binary strings are convereted into BigInt integers, then addition is performed and once again the conversion of the sum is to binary string. This is used to handle large binary numbers.

Syntax

let bigIntValue = BigInt(value);

JavaScript

let s1 = "101010";
let s2 = "1011";
let sum = (a, b) => {
    let decSum =
        BigInt(`0b${a}`) +
        BigInt(`0b${b}`);
    return decSum.toString(2);
};
console.log(sum(s1, s2));

Output

Using Manual Operation

The manual operations add the binary digits. We initially ensuring that both of the strings are of same length by adding them with leading 0s, and then iterating through the strings from left to right order and adding binary digits while considering the carry.

JavaScript

let str1 = "101010";
let str2 = "1011";
let sum = (m, n) => {
    let len = Math.max(
        m.length,
        n.length
    );
    m = m.padStart(len, "0");
    n = n.padStart(len, "0");
    let carry = 0;
    let res = "";

    for (let i = len - 1; i >= 0; i--) {
        let mBit = +m[i];
        let nBit = +n[i];
        let sum = mBit + nBit + carry;
        carry = Math.floor(sum / 2);
        res = (sum % 2) + res;
    }
    return carry ? "1" + res : res;
};
console.log(sum(str1, str2));

Output

Using Recursive Approach

The recursive approach adds two binary strings by breaking down the problem into smaller subproblems. It handles the binary addition bit-by-bit from the end, carrying over the extra bit when necessary, until the base case where one of the strings is empty.

JavaScript

function addBinary(a, b) {
    if (a.length < b.length) [a, b] = [b, a];
    if (b.length === 0) return a;
    if (a[a.length - 1] === '1' && b[b.length - 1] === '1') {
        return addBinary(addBinary(a.slice(0, -1), b.slice(0, -1)), '1') + '0';
    }
    if (a[a.length - 1] === '0' && b[b.length - 1] === '0') {
        return addBinary(a.slice(0, -1), b.slice(0, -1)) + '0';
    }
    return addBinary(a.slice(0, -1), b.slice(0, -1)) + '1';
}

console.log(addBinary("1010", "1011"));

Output

Using XOR and AND Bitwise Operators

This approach involves using bitwise operators XOR (^) and AND (&) to add two binary strings. The XOR operation helps in summing the bits without carrying over, while the AND operation helps in finding the carry bits. We then shift the carry bits to the left and repeat the process until there are no more carry bits left.

JavaScript

let str1 = "101010";
let str2 = "1011";

let addBinary = (a, b) => {
    let x = BigInt(`0b${a}`);
    let y = BigInt(`0b${b}`);
    
    while (y !== 0n) {
        let carry = x & y;
        x = x ^ y;
        y = carry << 1n;
    }
    
    return x.toString(2);
};

console.log(addBinary(str1, str2));

Output

Using Array Methods for Binary Addition

In this approach, we use array methods to perform binary addition. This involves converting the binary strings into arrays, iterating through them to perform the addition, and handling the carry. This method leverages the power of JavaScript array functions to simplify the process.

JavaScript

function binaryAddition(str1, str2) {
    // Ensure str1 is the longer string
    if (str2.length > str1.length) [str1, str2] = [str2, str1];

    // Convert strings to arrays
    let arr1 = str1.split('').reverse();
    let arr2 = str2.split('').reverse();

    let result = [];
    let carry = 0;

    // Iterate through the arrays and perform binary addition
    for (let i = 0; i < arr1.length; i++) {
        let bit1 = parseInt(arr1[i], 10);
        let bit2 = i < arr2.length ? parseInt(arr2[i], 10) : 0;

        let sum = bit1 + bit2 + carry;
        result.push(sum % 2);  // Remainder of sum divided by 2
        carry = Math.floor(sum / 2);  // Integer division of sum by 2
    }

    // If there's a carry left, add it to the result
    if (carry) result.push(carry);

    // Convert result array back to string and reverse it
    return result.reverse().join('');
}

// Example usage:
let binaryStr1 = "1101";
let binaryStr2 = "1011";
let sum = binaryAddition(binaryStr1, binaryStr2);
console.log(sum);  // Output: "11000"

Output

JavaScript Program to Add Two Binary Strings

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Article Tags :

JavaScript Program to Add Two Binary Strings

Using parseInt() and toString()

Syntax

2. Using BigInt Method

Syntax

Using Manual Operation

Using Recursive Approach

Using XOR and AND Bitwise Operators

Using Array Methods for Binary Addition

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