path: root/files/tr/web/javascript/reference/global_objects/array/findindex/index.html

---
title: Array.prototype.findIndex()
slug: Web/JavaScript/Reference/Global_Objects/Array/findIndex
translation_of: Web/JavaScript/Reference/Global_Objects/Array/findIndex
---
<div>{{JSRef}}</div>

<p>FindIndex () yöntemi, sağlanan test işlevini karşılayan dizideki ilk öğenin dizinini döndürür. Aksi takdirde -1 iade edilir.</p>

<div>{{EmbedInteractiveExample("pages/js/array-findindex.html")}}</div>

<p class="hidden">Bu interaktif örneğin için kaynak bir GitHub deposunda saklanır. Etkileşimli örnek projesine katkıda bulunmak isterseniz, lütfen https://github.com/mdn/interactive-examples klonlayın ve bize bir çekme isteği gönderin.</p>

<div> </div>

<p>Ayrıca, dizinde bulunan dizinin yerine bulunan bir öğenin değerini döndüren {{jsxref ("Array.find", "find ()")}} yöntemine de bakın.</p>

<h2 id="Syntax">Syntax</h2>

<pre class="syntaxbox"><var>arr</var>.findIndex(<var>callback</var>[, <var>thisArg</var>])</pre>

<h3 id="Parameters">Parameters</h3>

<dl>
 <dt><code>callback</code></dt>
 <dd>Function to execute on each value in the array, taking three arguments:
 <dl>
  <dt><code>element</code></dt>
  <dd>The current element being processed in the array.</dd>
  <dt><code>index</code>{{optional_inline}}</dt>
  <dd>The index of the current element being processed in the array.</dd>
  <dt><code>array</code>{{optional_inline}}</dt>
  <dd>The array <code>findIndex</code> was called upon.</dd>
 </dl>
 </dd>
 <dt><code>thisArg</code>{{optional_inline}}</dt>
 <dd>Optional. Object to use as <code>this</code> when executing <code>callback</code>.</dd>
</dl>

<h3 id="Return_value">Return value</h3>

<p>An index in the array if an element passes the test; otherwise, <strong>-1</strong>.</p>

<h2 id="Description">Description</h2>

<p>The <code>findIndex</code> method executes the <code>callback</code> function once for every array index <code>0..length-1</code> (inclusive) in the array until it finds one where <code>callback</code> returns a truthy value (a value that coerces to <code>true</code>). If such an element is found, <code>findIndex</code> immediately returns the index for that iteration. If the callback never returns a truthy value or the array's <code>length</code> is 0, <code>findIndex</code> returns -1. Unlike some other array methods such as Array#some, in sparse arrays the <code>callback</code> <strong>is</strong> called even for indexes of entries not present in the array.</p>

<p><code>callback</code> is invoked with three arguments: the value of the element, the index of the element, and the Array object being traversed.</p>

<p>If a <code>thisArg</code> parameter is provided to <code>findIndex</code>, it will be used as the <code>this</code> for each invocation of the <code>callback</code>. If it is not provided, then {{jsxref("undefined")}} is used.</p>

<p><code>findIndex</code> does not mutate the array on which it is called.</p>

<p>The range of elements processed by <code>findIndex</code> is set before the first invocation of <code>callback</code>. Elements that are appended to the array after the call to <code>findIndex</code> begins will not be visited by <code>callback</code>. If an existing, unvisited element of the array is changed by <code>callback</code>, its value passed to the visiting <code>callback</code> will be the value at the time that <code>findIndex</code> visits that element's index; elements that are deleted are still visited.</p>

<h2 id="Examples">Examples</h2>

<h3 id="Find_the_index_of_a_prime_number_in_an_array">Find the index of a prime number in an array</h3>

<p>The following example finds the index of an element in the array that is a prime number (or returns -1 if there is no prime number).</p>

<pre class="brush: js">function isPrime(element, index, array) {
  var start = 2;
  while (start &lt;= Math.sqrt(element)) {
    if (element % start &lt; 1) {
      return false;
    } else {
        start++;
    }
  }
  return element &gt; 1;
}

console.log([4, 6, 8, 12].findIndex(isPrime)); // -1, not found
console.log([4, 6, 7, 12].findIndex(isPrime)); // 2
</pre>

<h3 id="Find_index_using_arrow_function">Find index using arrow function</h3>

<p>The following example finds the index of a fruit using an arrow function.</p>

<pre class="brush: js">const fruits = ["apple", "banana", "cantaloupe", "blueberries", "grapefruit"];

const index = fruits.findIndex(fruit =&gt; fruit === "blueberries");

console.log(index); // 3
console.log(fruits[index]); // blueberries
</pre>

<h2 id="Polyfill">Polyfill</h2>

<pre class="brush: js">// 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 &gt;&gt;&gt; 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 &lt; len
      while (k &lt; 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;
    },
    configurable: true,
    writable: true
  });
}
</pre>

<p>If you need to support truly obsolete JavaScript engines that don't support <code><a href="/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty">Object.defineProperty</a></code>, it's best not to polyfill <code>Array.prototype</code> methods at all, as you can't make them non-enumerable.</p>

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('ES2015', '#sec-array.prototype.findindex', 'Array.prototype.findIndex')}}</td>
   <td>{{Spec2('ES2015')}}</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('ESDraft', '#sec-array.prototype.findIndex', 'Array.prototype.findIndex')}}</td>
   <td>{{Spec2('ESDraft')}}</td>
   <td> </td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<div>


<p>{{Compat("javascript.builtins.Array.findIndex")}}</p>
</div>

<h2 id="See_also">See also</h2>

<ul>
 <li>{{jsxref("Array.prototype.find()")}}</li>
 <li>{{jsxref("Array.prototype.indexOf()")}}</li>
</ul>