I have two arrays that I need to check the difference upon and return the sum of all elements of the array before the changed element and includes him.

I currently have two arrays of area height that get updated when the input's value is changed. Also can be changed 2 or more elements of array, then need sum all changed elements and all elements before last changed element.

For example arrays:

let oldArea = [3, 4, 2]

let newArea = [3, 6, 2]

I tried something like this (it does its job partially, but the array length can be 5 or more elements, so this solution is bad) :

let oldArea = [3, 4, 2]
let newArea = [3, 6, 2]

let changedArea = [];

if (
  oldArea[0] !== newArea[0] &&
  oldArea[1] === newArea[1]
) {
  changedArea.push(newArea[0]);
} else if (
  oldArea[1] !== newArea[1] &&
  oldArea[0] === newArea[0] &&
  oldArea[2] === newArea[2]
) {
  changedArea.push(newArea[0]   newArea[1]);
} else changedArea.push(newArea.reduce((a, b) => a   b, 0));

let changedAreaHeight = changedArea.reduce((a, b) => a   b, 0);

console.log(changedAreaHeight)

Example

I will be grateful for any tips with other solutions.

CodePudding user response：

You can use a simple for loop and break when the elements are not same

let oldArea = [3, 4, 2]
let newArea = [3, 6, 2]

let final = 0;

for (let i = 0; i < newArea.length; i  ) {
  if (newArea[i] === oldArea[i]) {
    final  = newArea[i]
  } else {
    final  = newArea[i]
    break;
  }
}

console.log(final)