javascript array methods find 28 29

1const inventory = [
2  {name: 'apples', quantity: 2},
3  {name: 'cherries', quantity: 8}
4  {name: 'bananas', quantity: 0},
5  {name: 'cherries', quantity: 5}
6  {name: 'cherries', quantity: 15}
7  
8];
9
10const result = inventory.find( ({ name }) => name === 'cherries' );
11
12console.log(result) // { name: 'cherries', quantity: 5 }

1// Use array.find() like this:
2
3var myArrayOfAges = [1,4,6,8,9,13,16,21,53,78];
4
5var result = myArrayOfAges.find(age => age >= 12);
6
7console.log(result); // Output: 13
8
9/* ------ Below is a polyfill from Mozilla: ------ */
10
11// https://tc39.github.io/ecma262/#sec-array.prototype.find
12if (!Array.prototype.find) {
13  Object.defineProperty(Array.prototype, 'find', {
14    value: function(predicate) {
15      // 1. Let O be ? ToObject(this value).
16      if (this == null) {
17        throw TypeError('"this" is null or not defined');
18      }
19
20      var o = Object(this);
21
22      // 2. Let len be ? ToLength(? Get(O, "length")).
23      var len = o.length >>> 0;
24
25      // 3. If IsCallable(predicate) is false, throw a TypeError exception.
26      if (typeof predicate !== 'function') {
27        throw TypeError('predicate must be a function');
28      }
29
30      // 4. If thisArg was supplied, let T be thisArg; else let T be undefined.
31      var thisArg = arguments[1];
32
33      // 5. Let k be 0.
34      var k = 0;
35
36      // 6. Repeat, while k < len
37      while (k < len) {
38        // a. Let Pk be ! ToString(k).
39        // b. Let kValue be ? Get(O, Pk).
40        // c. Let testResult be ToBoolean(? Call(predicate, T, « kValue, k, O »)).
41        // d. If testResult is true, return kValue.
42        var kValue = o[k];
43        if (predicate.call(thisArg, kValue, k, o)) {
44          return kValue;
45        }
46        // e. Increase k by 1.
47        k++;
48      }
49
50      // 7. Return undefined.
51      return undefined;
52    },
53    configurable: true,
54    writable: true
55  });
56}

1const list = [5, 12, 8, 130, 44];
2// a find metóduson belül a number egy paraméter
3// azért nem szükséges köré a zárójel, mert csak egy paramétert adunk át
4// minden más esetben így kell írni:
5// const found = list.find((index, number) => number > index);
6const found = list.find(number => number > 10);
7console.log(found);
8// --> 12