Documentation

Guides and references for all you need to know about Flow.

📄️ Introduction

Never used a type system before or just new to Flow? Let's get you up and running in a few minutes.

📄️ FAQ

Have a question about using Flow? Check here first!

📄️ Type Annotations

Learn how to add Flow type annotations to your code: Primitives, Objects, Functions, Classes, and more.

📄️ Type System

In JavaScript there are many types of values: numbers, strings, booleans,

📄️ React

Learn how to use Flow to effectively type common and advanced React patterns.

📄️ Flow Enums

Define a fixed set of constants which create their own type. Exhaustively checked in switch statements.

📄️ Match

match an input value against a series of patterns, which conditionally check the structure of the input and extract values, and either produce an expression (match expressions) or execute a block (match statements).

📄️ Declarations

Learn how to write types in .flow files.

📄️ Library Definitions

Learn how to create and use library definitions for the third-party code your code depends on.

📄️ Error Suppressions

Learn how to suppress Flow's type errors.

📄️ Linting

Learn how to configure Flow's linter to find potentially harmful code.

📄️ Flow Strict

Learn how to enable stricter type checking on a file-by-file basis.

📄️ Flow CLI

How to use Flow from the command line. Including how to manage the Flow background process.

📄️ Configuration

Flow tries to work out of the box as much as possible, but can be configured to work with any codebase.

📄️ Tools

Flow and Babel are designed to work great together. It

📄️ Editors

Detailed guides, tips, and resources on how to integrate Flow with different code editors.