JSFiddle - React, Tailwind, and code Playground

by Vladymyr Shevchuk

JavaScript

const arr = [20,10,-80,10,10,15,35];

function findEvenIndex(arr) {
  let result = -1;
  
  arr.forEach((item, index) => {
  	const leftSide = arr.slice(0, index);
    const rightSide = arr.slice(index + 1, arr.length + 1);
    
    const getSum = array => array.reduce((accum, item) => (accum + item), 0);
    
    console.error(leftSide);
    console.error(rightSide);
    
    if (getSum(leftSide) === getSum(rightSide)) {
      result = index;
    }
  });  
  
  return result;
}

console.error(findEvenIndex(arr))