some() and every()

Syntax

arr.some(item => condition)
arr.every(item => condition)

Examples

const numbers = [1, 3, 5, 8, 9];

console.log(numbers.some(n => n % 2 === 0)); // true - 8 is even
console.log(numbers.some(n => n > 100));      // false - none are

const ages = [22, 25, 30, 18];

console.log(ages.every(age => age >= 18)); // true - all are adults
console.log(ages.every(age => age >= 21)); // false - 18 fails the check

const formFields = [
  { name: "email", value: "user@test.com" },
  { name: "password", value: "" },
  { name: "username", value: "bob" }
];

const allFilled = formFields.every(field => field.value.length > 0);
console.log(allFilled); // false - password is empty

const hasEmptyField = formFields.some(field => field.value.length === 0);
console.log(hasEmptyField); // true

Best practices

• Use some() instead of filter().length > 0 when you only need a true/false answer - it stops early, which is more efficient
• Use every() for validation checks where all items must satisfy a rule, like confirming every required field is filled
• Remember every() on an empty array always returns true (vacuous truth), and some() on an empty array always returns false
• Combine some()/every() with logical operators for readable, declarative validation logic

At a glance

Purpose

Application logic and interaction

File extension

.js · .mjs

Runs in

Browsers and JavaScript runtimes

Usually used with

HTML, CSS and Web APIs

Specifications & further reading

• ECMAScript specification

Related JavaScript documentation