Why is using a loop to iterate from start of array to end faster than iterating both start to end and end to start?

Question

Given an array having .length 100 containing elements having values 0 to 99 at the respective indexes, where the requirem

Answer 1

Selected answer is excellent. I'd like to add another aspect: Try findIndex(), it's 2-3 times faster than using loops:

const arr = Array.from({length: 900}, (_, i) => i);
const n = 51;
const len = arr.length;

console.time("iterate from start");
for (let i = 0; i < len; i++) {
  if (arr[i] === n) break;
}
console.timeEnd("iterate from start");

console.time("iterate using findIndex");
var i = arr.findIndex(function(v) {
  return v === n;
});
console.timeEnd("iterate using findIndex");