function sumIndex(nums,target){
let map = new Map
for(let i=0;i<nums.length;i++){
let cha = target - nums[i]
if(map.has(cha)){
return [map.get(cha),i]
}else{
map.set(nums[i],i)
}
}
}
let nums = [2,9,7]
let target = 9
console.log(sumIndex(nums,target))