Array some() method

JavaScriptJunior~2 min read

some() is a logical array method that checks whether at least one element satisfies a condition and returns true or false. As soon as the first matching element is found the loop stops, so the method behaves as a fast existence check rather than a full scan.

Theory

TL;DR

some() returns true if at least one element satisfies the condition, otherwise false.
Iteration stops at the first match, the remaining elements are never checked.
For an empty array the result is always false.
The callback must return a value, otherwise the condition is always falsy.
some() means "at least one", every() means "all", find() returns the element itself, filter() returns an array.

Quick example

javascript

const numbers = [1, 3, 5, 6, 7];

const hasEven = numbers.some(num => num % 2 === 0);

console.log(hasEven); // true

some() returned true because the array contains at least one even number (6), and iteration stopped there.

Syntax and parameters

javascript

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

Callback parameters:

Argument	Description
`element`	the current array element
`index`	the index of the current element
`array`	the source array itself

Typical use cases

Checking whether there are any adult users. The method stops as soon as it finds the first adult user.

javascript

const users = [
  { name: 'Tim', age: 17 },
  { name: 'Alex', age: 21 },
  { name: 'John', age: 16 }
];

const hasAdult = users.some(user => user.age >= 18);

console.log(hasAdult); // true

Checking that a value is present.

javascript

const fruits = ['apple', 'banana', 'cherry'];

const hasBanana = fruits.some(fruit => fruit === 'banana');
console.log(hasBanana); // true

const hasMango = fruits.some(fruit => fruit === 'mango');
console.log(hasMango); // false

An empty array. There are no elements, so none of them can satisfy the condition.

javascript

console.log([].some(x => x > 0)); // false

A plain numeric illustration.

javascript

const arr = [1, 2, 3, 4, 5];

console.log(arr.some(x => x > 3)); // true
console.log(arr.some(x => x < 0)); // false

The difference between some() and every()

some() answers the question "is there at least one", while every() answers "are they all". Both bail out early: some() on the first true, every() on the first false.

javascript

const ages = [18, 22, 30, 16];

console.log(ages.some(age => age < 18));   // true, there is at least one minor
console.log(ages.every(age => age >= 18)); // false, not everyone is an adult

The edge case is worth remembering too: on an empty array some() gives false while every() gives true.

When to use some() and when to use other methods

Goal	Is `some()` a good fit
Check that at least one element matches a condition	Yes
Check that every element matches a condition	No, use `every()`
Get the element itself	No, use `find()`
Get the list of all matching elements	No, use `filter()`

A comparison with similar methods:

Method	What it returns	Condition	Does it stop at the first match
`some()`	`true / false`	at least one element matches	yes
`every()`	`true / false`	all elements match	yes, on the first `false`
`find()`	the element or `undefined`	at least one element matches	yes
`filter()`	a new array	all matching elements	no

A formula worth memorising: arr.some(condition) gives true or false.

Common mistakes

1. Expecting an array instead of a boolean.

javascript

const result = arr.some(x => x > 10);
console.log(result.length); // TypeError, some() returns true or false

2. A missing return in a callback with curly braces. The function returns undefined, which is falsy, so the result is always false.

javascript

arr.some(num => { num > 5 }); // always false

The fix:

javascript

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

3. Confusing some() with every(). some() means at least one element passes the condition, every() means all elements pass it. Swapping one for the other silently changes the logic of the check.

4. Using some() for side effects. The method is meant for checking, not for iterating with actions; use forEach() or a plain for...of for that.

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