object doesn't support property or method 'findIndex' IE11 javascript issue

Question

I have an AngularJS application that is giving me some issues in Internet Explorer 11 - In my administration area I am getting console log errors that seem to correlate with some problems I have noticed in the page with filtering data when using Internet Explorer (version 11 specifically) however fine in Chrome/Firefox etc.

Object doesn't support property or method 'findIndex' 
at Anonymous function (http://myapp.local/js/controllers/admin/UsersController.js:363:9)

When I navigate to this line in the code this is the section in question :-

[363]   var indexInOriginalSet = $scope.originalSet.findIndex(function(u) {
[364]        return u.id == userId;
[365]   });

What is the best solution to fix this IE problem with the findIndex?

Answer 1

you can use a polyfill, in partirular this one:

// https://tc39.github.io/ecma262/#sec-array.prototype.findIndex
if (!Array.prototype.findIndex) {
  Object.defineProperty(Array.prototype, 'findIndex', {
    value: function(predicate) {
     // 1. Let O be ? ToObject(this value).
      if (this == null) {
        throw new TypeError('"this" is null or not defined');
      }

      var o = Object(this);

      // 2. Let len be ? ToLength(? Get(O, "length")).
      var len = o.length >>> 0;

      // 3. If IsCallable(predicate) is false, throw a TypeError exception.
      if (typeof predicate !== 'function') {
        throw new TypeError('predicate must be a function');
      }

      // 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
      var thisArg = arguments[1];

      // 5. Let k be 0.
      var k = 0;

      // 6. Repeat, while k < len
      while (k < len) {
        // a. Let Pk be ! ToString(k).
        // b. Let kValue be ? Get(O, Pk).
        // c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
        // d. If testResult is true, return k.
        var kValue = o[k];
        if (predicate.call(thisArg, kValue, k, o)) {
          return k;
        }
        // e. Increase k by 1.
        k++;
      }

      // 7. Return -1.
      return -1;
    }
  });
}

You can find more details here

Answer 2

I wrote a little function to do that, what you want. It expects an array as first parameter and a filter-callback as second parameter.

var findIndex = function(arr, fn) {
    return arr.reduce(function(carry, item, idx) {
        if(fn(item, idx)) {
            return idx;
        }

        return carry;
    } , -1);
};

console.log(findIndex(arr, function(u) {
    return u.id == userId;
}));