JavaScript lesson · 18 min

JavaScript find, some, and every

Search arrays and ask yes/no questions with find, some, and every.

Code runs locally in your browser

What you will practice

Use find to get one matching item.
Use some to check whether at least one item matches.
Use every to check whether all items match.

What this means

Array search methods help you ask questions about a list without writing a full loop every time.

`find` returns the first item that matches a condition. `some` returns true when at least one item matches. `every` returns true only when all items match.

These methods use callback functions, so they are also good practice for reading callback-based code.

If this is your first time seeing this

These methods answer different questions about a list.

`find` gives you an item. `some` and `every` give you true or false.

Mini glossary

find: Returns the first array item that matches a condition.
some: Returns true when at least one item matches.
every: Returns true only when all items match.

Example from everyday life

Imagine checking a row of labeled boxes. `find` opens boxes until it finds the one you need. `some` asks whether any box contains a fragile item. `every` asks whether all boxes are sealed.

How it works step by step

The code creates a list of tools with names and readiness flags.
`find` returns the first server-side tool.
`some` checks whether at least one tool is not ready.
`every` checks whether every tool has a name.

Where you will use this

A product list finds one item by id.
A dashboard checks whether any task failed.
A form checks whether every required field has a value.

Before you run the code

Use these methods when the question is about existence or one matching item.

If you need a new list of all matching items, use `filter` instead of `find`.

Common beginner mistakes

Using `find` when you need all matching items. Use `filter` for that.
Forgetting that `find` can return `undefined` when nothing matches.
Mixing up `some` and `every` because both return booleans.

JavaScript editor

const tools = [
  { name: "JSON Formatter", privacy: "browser", ready: true },
  { name: "CORS Checker", privacy: "server", ready: true },
  { name: "Future Tool", privacy: "browser", ready: false }
];

const serverTool = tools.find((tool) => tool.privacy === "server");
const hasPlannedTool = tools.some((tool) => !tool.ready);
const allNamed = tools.every((tool) => tool.name.length > 0);

console.log(`Server tool: ${serverTool.name}`);
console.log(`Has planned tool: ${hasPlannedTool}`);
console.log(`All named: ${allNamed}`);

Console output

Run the code to see console output here.

Exercise checks0 of 2 checks passed.

WaitingFinds one matching item

WaitingAnswers a yes/no array question

Code runs locally in a temporary browser worker with a timeout. It is not sent to Lumio analytics or executed on the server.

Try changing this next

Change the server tool privacy to `browser` and see what happens.
Add another planned tool.
Make one tool name empty and check `All named`.

Previous lesson Next lesson