three_sum.js

var threeSum = function (nums) {
 // Sort the array
 nums.sort((a, b) => a - b);
 // Length of the array
 const n = nums.length;
 // Resultant list
 const triplets = [];
 // Loop for each element of the array
 for (let i = 0; i < n; i++) {
 // Skip the duplicates
 if (i > 0 && nums[i] === nums[i - 1]) {
 continue;
 }
 // Left and right pointers
 let j = i + 1;
 let k = n - 1;
 // Loop for all the remaining pairs
 while (j < k) {
 if (nums[i] + nums[j] + nums[k] === 0) {
 triplets.push([nums[i], nums[j], nums[k]]);
 j++;
 // Never let j refer to the same value twice (in an output) to avoid duplicates
 while (j < k && nums[j] === nums[j - 1]) {
 j++;
 }
 } else if (nums[i] + nums[j] + nums[k] < 0) {
 j++;
 } else {
 k--;
 }
 }
 }
 return triplets;
};

console.log(threeSum([-1, 0, 1, 2, -1, -4]));
console.log(threeSum([]));