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This is a new technology, part of the ECMAScript 2015 (ES6) standard.
This technology's specification has been finalized, but check the compatibility table for usage and implementation status in various browsers.

Podsumowanie

Metoda find() zwraca pierwszy element tablicy, który spełnia warunek podanej funkcji testującej. W przeciwnym razie, gdy żaden element tablicy nie spełni warunku, zwracana jest wartość undefined.

function isBigEnough(element) {
  return element >= 15;
}

[12, 5, 8, 130, 44].find(isBigEnough); // 130

Zobacz także metodę findIndex(), która zwraca indeks znalezionego elementu zamiast jego wartości.

Składnia

arr.find(callback[, thisArg])

Parametry

callback
Funkcja do wykonania przy każdym elemencie tablicy, przyjmująca trzy wartości
element
Element obecnie przetwarzany przez funkcję.
index
Indeks obecnie przetwarzanego elementu.
array
Tablica, na której wywołano funkcję find.
thisArg
Opcjonalny. Obiekt, który będzie się znajdował pod this w czasie wykonywania funkcji callback.

Description

The find method executes the callback function once for each element present in the array until it finds one where callback returns a true value. If such an element is found, find immediately returns the value of that element. Otherwise, find returns undefined. callback is invoked only for indexes of the array which have assigned values; it is not invoked for indexes which have been deleted or which have never been assigned values.

callback is invoked with three arguments: the value of the element, the index of the element, and the Array object being traversed.

If a thisArg parameter is provided to find, it will be used as the this for each invocation of the callback. If it is not provided, then undefined is used.

find does not mutate the array on which it is called.

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

Examples

Example: Find a prime number in an array

The following example finds an element in the array that is a prime number (or returns undefined if there is no prime number).

function isPrime(element, index, array) {
  var start = 2;
  while (start <= Math.sqrt(element)) {
    if (element % start++ < 1) {
      return false;
    }
  }
  return element > 1;
}

console.log([4, 6, 8, 12].find(isPrime)); // undefined, not found
console.log([4, 5, 8, 12].find(isPrime)); // 5

Polyfill

This method has been added to the ECMAScript 6 specification and may not be available in all JavaScript implementations yet. However, you can polyfill Array.prototype.find with the following snippet:

if (!Array.prototype.find) {
  Array.prototype.find = function(predicate) {
    if (this == null) {
      throw new TypeError('Array.prototype.find called on null or undefined');
    }
    if (typeof predicate !== 'function') {
      throw new TypeError('predicate must be a function');
    }
    var list = Object(this);
    var length = list.length >>> 0;
    var thisArg = arguments[1];
    var value;

    for (var i = 0; i < length; i++) {
      value = list[i];
      if (predicate.call(thisArg, value, i, list)) {
        return value;
      }
    }
    return undefined;
  };
}

Specifications

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Array.prototype.find' in that specification.
Standard Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 45.0 25.0 (25.0) No support No support 7.1
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support No support No support 25.0 (25.0) No support No support iOS 8

See also

Autorzy i etykiety dokumentu

 Autorzy tej strony: gpluta, kdex, svantetic, karol-f, thigrand
 Ostatnia aktualizacja: gpluta,