SOURCE

function twoSum(nums,target){
    const map=new Map()
    for(let i=0;i<nums.length;i++){
        const complete=target-nums[i]
        if(map.has(complete)){
            return [map.get(complete),i]
        }else{
            map.set(nums[i],i)
        }
    }
}
console.log(twoSum([3,1,4,6],9))