function sum (a, target) {
const sum = {}
let diffIndex = null
for (let key in a) {
const diff = target - a[key]
if (key) {
diffIndex = Object.values(sum).findIndex(val => val === diff)
}
if (!diffIndex) {
sum[key] = target - a[key]
} else {
return [key, diffIndex]
}
}
// console.log(sum)
}
console.log(sum([2, 7, 11, 15], 9))
// console.log(Object.values({}))
// console.log([].findIndex(1))
// let obj = { name: 1, age: 2 }
// console.log(Object.values(obj))
// const arr = Object.values(obj)
// console.log(arr.findIndex(val => val === 1))