Find the Indices of Two Numbers From an Array Whose Sum is Equal to the Target

leet-code-two-sum.js

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(nums, target) {
    
    let lookUp = {}
    
    for(let i = 0; i < nums.length; i++) {
        
        let complement = target - nums[i];
        
        if(lookUp[complement] !== undefined){
            return [lookUp[complement], i]
        }
        
        lookUp[nums[i]] = i;
    }
};