Solution.js

/**
 *  Author: limbowandering
 */

const twoSum = function (nums, target) {
    const map = {};
    for (let i = 0; i < nums.length; i++) {
        if (map[nums[i]] !== undefined) {
            return [map[nums[i]], i];
        } else {
            map[target - nums[i]] = i;
        }
    }
};

/**
 *  Author: Mcnwork2018
 */

var twoSum = function (nums, target) {
    let len = nums.length;
    let n = {};
    for (let i = 0; i < len; i++) {
        if (n[target - nums[i]] !== undefined) {
            return [n[target - nums[i]], i];
        }
        n[nums[i]] = i;
    }
};

/**
 * Author: rookie
 */

var twoSum = function (nums, target) {
    const map = new Map();
    for (let i = 0; i < nums.length; i++) {
        if (map.has(target - nums[i])) {
            return [map.get(target - nums[i]), i];
        }
        map.set(nums[i], i);
    }
    return [];
};