Kata

binaryToString.js

function binaryToString(binary) {

    // Split for readability, though it could be in-lined too
    const binaryToInteger = (string) => {
        let final = 0;
        for (let i = string.length - 1, digits = string.split(''), exp = 1; i >= 0; i--) {
            final += +digits[i] * exp;
            // Bit shift left by 1 i.e. 1, 2, 4, 8, 16, 32, 64....
            exp <<= 1;
        }

        return final;
    };

    // Split into 8bit chunks and map to an array that is then joined
    return binary === '' ? binary : binary.match(/([01]{8})/g).map((chunk) => {
        return String.fromCharCode(binaryToInteger(chunk));

    // Join to make a string
    }).join('');

}

// Example

console.log(binaryToString('01100001'), 'a');

ipToNum.js

function ipToNum(ip) {
    // Readability only!
    const BINARY_LENGTH = 8;

    return parseInt(ip.split('.').map((segment) => {
        // +segment is a trick to parse as an integer
        const binary = (+segment).toString(2);

        // Ensure the length is 8 bits (leading zeros are stripped basically)
        return new Array(BINARY_LENGTH - binary.length + 1).join('0') + binary;
    }).join(''), 2); // 2 equals from binary
}

function numToIp(num) {
    // Readability only!
    const BINARY_LENGTH = 32;

    // Sometimes this returns 31 bits or less and NOT 32 bits (leading zeros are stripped basically), so we have to pre-append zeros
    num = num.toString(2);

    return (new Array(BINARY_LENGTH - num.length + 1).join('0') + num).match(/[01]{8}/g).map((segment) => {
        return parseInt(segment, 2).toString(10); // 2 equals from binary to decimal (10)
    }).join('.');
}

// Example
console.log(ipToNum('192.168.1.1'));
console.log(numToIp(ipToNum('192.168.1.1')));