What is the functionality of this JavaScript code after the "if" statement?

I am having trouble understanding how this code works, especially after the if(y in hash) statement. I don't see any values being pushed into hash initially. Can someone explain what happens behind the scenes and the significance of y in hash?

var twoSum = function(nums, target) {

  const hash = {}
  
  for (const i in nums) {
    const x = nums[i];
    const y = target - x
    if (y in hash)
      return [i, hash[y]]
    hash[x] = i
  }

}

let arr = [2, 3, 4, 5, 6]
console.log(twoSum(arr, 11))

javascriptarraysobject

Answer №1

The hash is currently empty and I am not adding any values to it.

When I use hash[x] = i, it adds values to the hash because it falls outside of the if(y in hash) condition.

What does y in hash mean?

As mentioned by Nick Parsons in a comment, "it checks if the key stored in y exists in the hash object (or its prototype chain)."

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