function findIndex(arr, prop, value) {
    // use native findIndex if supported
    if (Array.prototype.findIndex) {
      return arr.findIndex(function (cur) {
        return cur[prop] === value;
      });
    }

    // use `find` + `indexOf` if `findIndex` isn't supported
    var match = find(arr, function (obj) {
      return obj[prop] === value;
    });
    return arr.indexOf(match);
  }
Return the index of the matching object
@method
@memberof Popper.Utils
@argument {Array} arr
@argument prop
@argument value
@returns index or -1