list.js/src/utils/index-of.js

The perfect library for lists. Supports search, sort, filters and flexibility. Built to be invisible and work on existing HTML

var indexOf = [].indexOf

module.exports = function(arr, obj){
  if (indexOf) return arr.indexOf(obj);
  for (var i = 0, il = arr.length; i < il; ++i) {
    if (arr[i] === obj) return i;
  }
  return -1
}