find and some

Learn search and check with .find and .some.

find and some

The find method returns the first element that matches a condition. If nothing matches, it returns undefined. Use find when you want only the first match, not all of them.

The some method asks whether at least one element matches. It does not return an array; it returns true or false. Use some when you care about existence, not the element itself.

Example: [1, 2, 3].find(n => n > 1) returns 2. [1, 2, 3].some(n => n > 2) returns true because 3 matches.

some versus every

The sibling of some is every. While some returns true when at least one element matches, every returns true only when all of them do. Both return a boolean, not an array.

On an empty array, some always returns false and every always returns true. This is a logical rule: with no items, the 'at least one' claim is false, while the 'all' claim is vacuously true.

Example: [2, 4, 6].every(n => n % 2 === 0) returns true because all are even. [1, 2, 3].every(n => n % 2 === 0) returns false.

Exercise Find a user

Define an array of users [{name:"Ayşe",age:30}, {name:"Alex",age:17}, {name:"Mara",age:25}]. Use find to get the first user whose age is at least 18, and print that user's name with console.log.

Show example solution

const users = [{name:'Ayşe',age:30}, {name:'Alex',age:17}, {name:'Mara',age:25}];
const adult = users.find(u => u.age >= 18);
console.log(adult.name);

Test yourself

What does find return?
- true
- The first matching element
- All matches
- A new array
Show answer

The first matching element — find returns the first element that matches.

Is anyone an adult?

const ages = [12, 17, 21];
const hasAdult = ages.some(age => age ____ 18);

Show answer

const ages = [12, 17, 21];
const hasAdult = ages.some(age => age >= 18);

Match the methods

find

First matching element
some

Is there at least one match
every

Do all items match
undefined

find's result when nothing matches

Next lesson: forEach

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