https://leetcode.com/problems/similar-rgb-color

Similar Colors.js

/**
 * @param {string} color
 * @return {string}
 */

const doubles = new Array(16).fill(0).map((_, i) => i * 17);

var similarRGB = function(color) {
    const red = binarySearch(doubles, toRGB(color));
    const blue = binarySearch(doubles, toRGB(color, 2));
    const green = binarySearch(doubles, toRGB(color, 4));
        
    return `#${toHex(red)}${toHex(blue)}${toHex(green)}`;
};

function toHex(val) {
    if (val === 0) {
        return '00';
    }
    
    return val.toString(16);
}

function binarySearch(arr, val, start = 0, end = arr.length - 1) {
    while (start <= end) {
        const mid = Math.floor((start + end) / 2);
        if (arr[mid] > val) {
            end = mid - 1;
        } else if (arr[mid] < val) {
            start = mid + 1;
        } else {
            return arr[mid];
        }
    }
    
    return Math.abs(val - arr[end]) < Math.abs(val - arr[start]) ? arr[end] : arr[start];
}

function toRGB(hex, offset = 0) {
    return parseInt(hex.substr(offset + 1, 2), 16);
}