find() in an array

JavaScriptJunior~2 min read

The find() method is one of the most commonly used methods in JavaScript for finding a specific element in an array by a condition. It does not filter or iterate the whole array to build a new one - it finds the first matching element and stops.

Syntax

javascript

const result = array.find((element, index, array) => {
  return condition;
});

Callback parameters:

Argument	Description
`element`	The current array element
`index`	The index of the current element
`array`	The original array itself

Example 1. Finding a number in an array

javascript

const numbers = [1, 5, 10, 15, 20];

const found = numbers.find(num => num > 10);

console.log(found); // 15

find() returned the first value satisfying the condition (> 10) and stopped searching. If nothing is found, it returns undefined.

Example 2. Finding an object by property

javascript

const users = [
  { id: 1, name: 'Tim', age: 25 },
  { id: 2, name: 'Alex', age: 17 },
  { id: 3, name: 'John', age: 30 }
];

const user = users.find(u => u.id === 3);

console.log(user);
// { id: 3, name: 'John', age: 30 }

A very common case - finding an element in an array of objects (for example, by id).

Example 3. When the element is not found

javascript

const arr = [10, 20, 30];
const res = arr.find(num => num > 50);

console.log(res); // undefined

If no matching element is found, undefined is returned, not an error.

Frequent mistakes

Expecting an array instead of a single element:

javascript

const result = arr.find(num => num > 5);
console.log(result.length); // Error - find returns an element, not an array

If you need all matching elements, not just one, use filter().

Forgotten return in curly braces:

javascript

arr.find(num => { num > 5 }); // always undefined

Correct:

javascript

arr.find(num => num > 5);
// or
arr.find(num => { return num > 5 });

When to use `find()`

Goal	Does `find()` fit
Find the first element satisfying the condition	Yes
Find all matching elements	No - use `filter()`
Check whether at least one element exists	No - use `some()`
Transform the data	No - use `map()`

In short:

find() returns the first element that satisfies the condition, or undefined if there is none.

Formula to remember: arr.find(condition) -> one_element_or_undefined

Comparison with similar methods

Method	What it returns	When it stops	Example
find()	The first matching element	After the first match	`[1,2,3].find(x => x>1)` -> `2`
filter()	All matching elements (an array)	After going through the whole array	`[1,2,3].filter(x => x>1)` -> `[2,3]`
findIndex()	Index of the found element	After the first match	`[10,20,30].findIndex(x=>x>10)` -> `1`
some()	`true`/`false` (whether at least one was found)	After the first match	`[1,2,3].some(x=>x>2)` -> `true`

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