Array.prototype.find()

The find() method of Array instances returns the first element in the provided array that satisfies the provided testing function. If no values satisfy the testing function, undefined is returned.

If you need the index of the found element in the array, use findIndex().
If you need to find the index of a value, use indexOf(). (It's similar to findIndex(), but checks each element for equality with the value instead of using a testing function.)
If you need to find if a value exists in an array, use includes(). Again, it checks each element for equality with the value instead of using a testing function.
If you need to find if any element satisfies the provided testing function, use some().

Syntax

find(callbackFn)
find(callbackFn, thisArg)

Parameters

callbackFn
- : A function to execute for each element in the array. It should return a truthy value to indicate a matching element has been found, and a falsy value otherwise. The function is called with the following arguments:
  - element
    - : The current element being processed in the array.
  - index
    - : The index of the current element being processed in the array.
  - array
    - : The array find() was called upon.
thisArg
- : A value to use as this when executing callbackFn. See iterative methods.

Return value

The first element in the array that satisfies the provided testing function. Otherwise, undefined is returned.

Description

The find() method is an iterative method. It calls a provided callbackFn function once for each element in an array in ascending-index order, until callbackFn returns a truthy value. find() then returns that element and stops iterating through the array. If callbackFn never returns a truthy value, find() returns undefined.

callbackFn is invoked for every index of the array, not just those with assigned values. Empty slots in sparse arrays behave the same as undefined.

find() does not mutate the array on which it is called, but the function provided as callbackFn can. Note, however, that the length of the array is saved before the first invocation of callbackFn. Therefore:

callbackFn will not visit any elements added beyond the array's initial length when the call to find() began.
Changes to already-visited indexes do not cause callbackFn to be invoked on them again.
If an existing, yet-unvisited element of the array is changed by callbackFn, its value passed to the callbackFn will be the value at the time that element gets visited. Deleted elements are visited as if they were undefined.

Warning: Concurrent modifications of the kind described above frequently lead to hard-to-understand code and are generally to be avoided (except in special cases).

The find() method is generic. It only expects the this value to have a length property and integer-keyed properties.

Examples

Find an object in an array by one of its properties

const inventory = [
  { name: "apples", quantity: 2 },
  { name: "bananas", quantity: 0 },
  { name: "cherries", quantity: 5 },
];

function isCherries(fruit) {
  return fruit.name === "cherries";
}

console.log(inventory.find(isCherries));
// { name: 'cherries', quantity: 5 }

Using arrow function and destructuring

const inventory = [
  { name: "apples", quantity: 2 },
  { name: "bananas", quantity: 0 },
  { name: "cherries", quantity: 5 },
];

const result = inventory.find(({ name }) => name === "cherries");

console.log(result); // { name: 'cherries', quantity: 5 }

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) {
  let 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

Using find() on sparse arrays

Empty slots in sparse arrays are visited, and are treated the same as undefined.

// Declare array with no elements at indexes 2, 3, and 4
const array = [0, 1, , , , 5, 6];

// Shows all indexes, not just those with assigned values
array.find((value, index) => {
  console.log("Visited index", index, "with value", value);
});
// Visited index 0 with value 0
// Visited index 1 with value 1
// Visited index 2 with value undefined
// Visited index 3 with value undefined
// Visited index 4 with value undefined
// Visited index 5 with value 5
// Visited index 6 with value 6

// Shows all indexes, including deleted
array.find((value, index) => {
  // Delete element 5 on first iteration
  if (index === 0) {
    console.log("Deleting array[5] with value", array[5]);
    delete array[5];
  }
  // Element 5 is still visited even though deleted
  console.log("Visited index", index, "with value", value);
});
// Deleting array[5] with value 5
// Visited index 0 with value 0
// Visited index 1 with value 1
// Visited index 2 with value undefined
// Visited index 3 with value undefined
// Visited index 4 with value undefined
// Visited index 5 with value undefined
// Visited index 6 with value 6

Calling find() on non-array objects

The find() method reads the length property of this and then accesses each property whose key is a nonnegative integer less than length.

const arrayLike = {
  length: 3,
  "-1": 0.1, // ignored by find() since -1 < 0
  0: 2,
  1: 7.3,
  2: 4,
};
console.log(Array.prototype.find.call(arrayLike, (x) => !Number.isInteger(x)));
// 7.3