what is index of javascript code example

Example 1: javascript index of with var

var indices = [];
var array = ['a', 'b', 'a', 'c', 'a', 'd'];
var element = 'a';
var idx = array.indexOf(element);
while (idx != -1) {
  indices.push(idx);
  idx = array.indexOf(element, idx + 1);
}
console.log(indices);
// [0, 2, 4]

Example 2: JS, indexOf();

function quickCheck(arr, elem) {
  return arr.indexOf(elem) != -1;
}
console.log(quickCheck(["squash", "onions", "shallots"], "mushrooms"));