Adding Flow
Flow, a formidable static type checker, stands ready to protect your code from lurking bugs. Fear not, for we shall guide you on this thrilling journey into the realm of static types in JavaScript. If you are new to this concept, fear not! Delve into this enchanting introduction to discover the power of static types.
Recent versions of Flow seamlessly integrate with Create React App projects.
Introduction:β
Welcome, aspiring Code Masterminds, to the magical world of Create React App! In this guide, we will delve into the realm of type checking and unveil the powers of Flow to bring order and certainty to your React applications. Prepare to embark on an adventure of static typing and fearless coding!
1: Introducing Flow - The Guardian of Typesβ
Meet Flow, a stalwart guardian bestowed upon us by the ancient sorcerers at Facebook. Flow is a static type checker that adds an extra layer of protection to your JavaScript code, ensuring that it adheres to predefined types and preventing sneaky bugs from infiltrating your app.
2: Unleashing Flow in Your Create React App (Dance of Installation)β
Let us begin our quest by integrating Flow into your Create React App project. Fear not, for the path is straightforward.
Prepare to summon Flow into your Create React App project by performing a few delicate steps:
- Utter the incantation
npm install --save flow-bin
(oryarn add flow-bin
) to add Flow to your magical dependencies. - Inscribe the sacred command
"flow": "flow"
into thescripts
section of yourpackage.json
to harness Flow's power. - Invoke the initiation ritual
npm run flow init
(oryarn flow init
) to conjure a.flowconfig
file at your project's core. - Fortify your code with the mark of Flow -
// @flow
. Bestow this incantation upon any files you wish to bless with type checking, such assrc/App.js
.
3: Unleashing the Magicβ
Behold the power Flow bestows upon you! With a simple command, npm run flow
(or yarn flow
), Flow will roam through your files, inspecting for lurking bugs and ensuring harmony among types.
Let us not forget the comforts of modern coding. Embrace extensions like Flow Language Support for Visual Studio Code or the wondrous Language Server Protocol standard (e.g. vim LSP) to receive hints as you weave your code.
4: The Elegance of Absolute Importsβ
Should you seek the elegance of absolute imports while dancing with Flow, heed this secret. Enchant your .flowconfig
with the following:
[options]
+ module.name_mapper='^\([^\.].*\)$' -> '<PROJECT_ROOT>/src/\1'
Let the magic of this incantation make Flow aware of your desires.
5: Casting Spells - Annotating Your Code with Typesβ
Now that Flow is up and running, it's time to adorn your code with type annotations. Brace yourself, for the power of type annotations will make your code more robust and comprehensible.
// @flow
function addNumbers(a: number, b: number): number {
return a + b;
}
const result: number = addNumbers(4, 5);
Observe how the number
type annotations indicate that a
and b
are expected to be numbers, and the function itself will return a number. Flow will diligently check if the types match during development, sparing you the anguish of runtime errors.