JavaScriptArraysBeginner

Array.find()

Returns the first element that matches a predicate, or undefined.

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array.find(predicateFn, thisArg?)
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What it does

Overview

Returns the first element that matches a predicate, or undefined.

The find() method executes a provided predicateFn once for each index of the array until it finds one where the function returns a truthy value. If such an element is found, find() immediately returns the value of that element; otherwise, it returns undefined. Because it short-circuits upon finding a match, it is more performant than Array.prototype.filter() when searching for a single unique record. It iterates over all indices, including 'holes' in sparse arrays (treating them as undefined), which distinguishes it from some older ES5 methods. Note that find() does not mutate the array on which it is called, but the predicateFn can. For performance-critical applications with large datasets, remember that the worst-case complexity is O(N). Internet Explorer (IE) is not supported.

Quick reference

Syntax

array.find(predicateFn, thisArg?)

Inputs

Parameters

predicateFunction · Returns true for the desired element.
thisArg (optional)any · Value used as 'this' inside predicate.

See it in practice

Examples

1

Finding an object by property

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

const result = inventory.find(function(item) {
  return item.name === 'cherries';
});

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

A common use case for finding a specific object within a collection based on a unique key.

2

Short-circuiting on first match

const numbers = [5, 12, 8, 130, 44];
const found = numbers.find(function(element) {
  return element > 10;
});

console.log(found);
Output:
12

Even though 130 and 44 also satisfy the condition, find() stops as soon as it encounters 12.

3

Handling missing elements

const scores = [10, 20, 30];
const highscore = scores.find(function(s) {
  return s > 100;
});

console.log(highscore);
Output:
undefined

When no element satisfies the predicate, the method returns undefined rather than throwing an error.

Debug faster

Common Errors

1

TypeError

Cause: Attempting to access a property on the result of find() when no match was found.

Fix: Check if the result is defined before accessing properties, or use optional chaining if the environment supports it.

const user = users.find(u => u.id === 999); 
// Error: Cannot read property 'name' of undefined
console.log(user.name);
2

LogicError

Cause: Confusing find() with filter() and expecting an array result.

Fix: Use filter() if you need all matching elements in an array, or find() if you only need the first single element.

const matches = [1, 2, 3].find(n => n > 0);
// matches is 1, not [1, 2, 3]
console.log(matches.length); // undefined

Runtime support

Compatibility

Node.js, BrowserAll modern browsers, IE not supportedES6 (2015)

Source: MDN Web Docs

Common questions

Frequently Asked Questions

Returns the first element that matches a predicate, or undefined.

predicate: Returns true for the desired element. thisArg: Value used as 'this' inside predicate.

TypeError: Check if the result is defined before accessing properties, or use optional chaining if the environment supports it. LogicError: Use filter() if you need all matching elements in an array, or find() if you only need the first single element.