index of in js code example

Example 1: 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

Example 2: .index of javascript

let monTableau = ['un', 'deux','trois', 'quatre'] ;
console.log(monTableau.indexOf('trois')) ;