All Aboard the Type Train

Kadi Kraman

@kadikraman

Formidable

Frontend

Backend

👑

Frontend

Backend

Why board the type train at all? 🚂

2. reduce production errors

1. communicate intent


  const sum = (a, b) => a + b;

  sum(2, 6);

  const sum = (a, b) => a + b;

  sum(2, 6);

// 8


  const sum = (a, b) => a + b;

  sum(2, "potato");

  const sum = (a, b) => a + b;

  sum(2, "potato");

// "2potato"


  const sum = (a, b) => a + b;

  sum(undefined, null);

  const sum = (a, b) => a + b;

  sum(undefined, null);

// NaN


  const sum = (a, b) => a + b;

  sum(undefined, null);

// NaN


  sum(2, "potato");

// "2potato"


  sum(2, 6);

// 8


  const addOne = array => array.map(val => val + 1);

  addOne([1, 2, 3])

  const addOne = array => array.map(val => val + 1);

  addOne([1, 2, 3])

// [2, 3, 4]


  const addOne = array => array.map(val => val + 1);

  addOne({})

  const addOne = array => array.map(val => val + 1);

  addOne({})
  /**
  * Adds together two numbers
  * @param a (number): first number to add
  * @param b (number): second number to add
  */
  const sum = (a, b) => a + b;

I could add some comments?

Just kidding - no one reads comments


  const sum = (a: number, b: number): number => a + b;

I could add explicit type information?

All programming languages have a type system

The difference is when the type-checking is done

Statically vs Dynamically typed language

Compile time

Run time

Static vs Dynamic

Static vs Dynamic

Types are checked before run-time

Go, C#, Haskell

Compile time

Run time

Static vs Dynamic

Types are checked before run-time

Types are checked at run-time, during execution

Go, C#, Haskell

Python, Lua, Obj C

Run time

Compile time

Types are checked before run-time

Types are checked at run-time, during execution

JavaScript is a

Dynamically Typed

language

Compile time

Run time

"Adding types to JavaScript"

"Checking types before runtime"

means

How to make JavaScript more type-safe?

Statically typed language that compiles to JavaScript

Static code analysis

1.

2.

Should you use Flow or TypeScript?

... or something else entirely!

Flow vs TypeScript

Flow - like eslint, but for types

TypeScript - a statically typed language

Flow

Infer type information from existing code

Flow

TypeScript

Infer type information from existing code

Flow

You can choose to enforce types

Flow

TypeScript

You can choose to enforce types

"Opt in" by adding a flow declaration at the top of the file

Adding to an existing codebase

Flow

TypeScript

TS is a superset of JS (so any valid JS file is also a valid TS file)

But you should change the file extensions to .ts and .tsx

Configuration

Flow

TypeScript

Performance

Flow

TypeScript

Slow to recompile on large projects

😱

Usually fast, but notoriously unstable

Community and typing node_modules

Flow

TypeScript

So should I use Flow or TypeScript?

🙅‍♀️

  • Larger community
  • Faster release cycle
  • More reliable
  • Easier to set up
  • More strict

One Big Flaw

Ignore type information

Both Flow and Typescript allow you to

😱

"Why not just use a proper statically typed language?"

🤓

ReasonML (2016 by Jordan Walke)

(Transpiles to OCaml which compiles to JS)


  let add = (x: int, y: int) : int => x + y;

✅ static code analysis

✅ statically typed

Elm (2012 by Evan Czaplicki)

  add : Number -> Number -> Number
  add a b =
    a + b

"no runtime exceptions"

(compiles to JS)

✅ static code analysis

✅ statically typed

New project, who dis?

Reliability in prod

Effort to learn

JavaScript

New project, who dis?

Reliability in prod

Effort to learn

JavaScript

Flow

Reason

Elm

TypeScript

New project, who dis?

Reliability in prod

Effort to learn

JavaScript

Flow

Reason

Elm

TypeScript

New project, who dis?

Reliability in prod

Effort to learn

JavaScript

Flow

Reason

Elm

TypeScript

Thank You 🤗

All Aboard the Type Train

By Kadi Kraman

All Aboard the Type Train

JavaScript is a language of add-ons, and one of its more recent trends is typing. There are obvious benefits to typing, but what are the drawbacks? Should you choose Flow or TypeScript? Why use types at all? And why not just go straight to Reason?

  • 67
Loading comments...

More from Kadi Kraman