how to use indexof with arrays code example

Example 1: js get index of item in array

array.indexOf("item");

Example 2: make indexOF in js

function indexOf(arr, value) {
  for (let [i, e] of arr.entries()) {
    if (value == e) return i;
  }
  return -1;
}
indexOf([1,2,3], 2);                     //returns 1