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SCALA.JS

1.10.0

A SAFER WAY TO BUILD ROBUST
FRONT-END WEB APPLICATIONS!

Learn Scala.js Try Scala.js in the browser

CORRECTNESS

Strong typing guarantees your code is free of silly mistakes; no more mixing up
strings or numbers, forgetting what keys an object has, or worrying about typos
in your method names. Scala.js takes care of all this tedious book-keeping for
you, letting you focus on the actual, more interesting problem your application
is trying to solve.

PERFORMANCE

Scala.js optimizes your Scala code into highly efficient JavaScript. Incremental
compilation guarantees speedy (1-2s) turn-around times when your code changes.
The generated JavaScript is both fast and small, starting from 45kB gzipped for
a full application.

INTEROPERABILITY

Scala.js loves JavaScript libraries, including React and AngularJS. You can use
any JavaScript library right from your Scala.js code, either in a statically or
dynamically typed way. You won't even notice you're crossing a language border!
Learn more.

EXCELLENT EDITOR SUPPORT

With Scala.js, typos and type-errors are immediately caught and shown to you in
your editor, without even needing to compile your code. Refactor any field or
method with ease, with the confidence that if you mess it up the editor will
tell you immediately. Stop flipping back and forth between your editor and MDN,
because your editor will display what methods are available, what arguments they
take, what they return, and even their documentation, right in-line with your
code!



GO BEYOND JAVASCRIPT ES6, TODAY

 * JavaScript/ES5
 * ECMAScript 6
 * TypeScript

HELLO WORLD!

JAVASCRIPT

console.log("Hello World!");

ECMASCRIPT 6

console.log("Hello World!");

TYPESCRIPT

console.log("Hello World!");

SCALA.JS

println("Hello World!")

CLASSES

JAVASCRIPT

var Person = function(firstName, lastName) {
  this.firstName = firstName;
  this.lastName = lastName;
};

Person.prototype.fullName = function() {
  return this.firstName + " " + this.lastName;
};

ECMASCRIPT 6

class Person {
  constructor(firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
  }

  fullName() {
    return `${this.firstName} ${this.lastName}`;
  }
}

TYPESCRIPT

class Person {
  constructor(public firstName: string,
      public lastName: string) {
  }

  fullName() {
    return `${this.firstName} ${this.lastName}`;
  }
}

SCALA.JS

class Person(val firstName: String, val lastName: String) {
  def fullName(): String =
    s"$firstName $lastName"
}

FAT ARROW FUNCTIONS

JAVASCRIPT

var names = persons.map(function(p) {
  return p.firstName;
});

ECMASCRIPT 6

const names = persons.map(p => p.firstName);

TYPESCRIPT

const names = persons.map(p => p.firstName);

SCALA.JS

val names = persons.map(p => p.firstName)
// or an even shorter version
val names = persons.map(_.firstName)

COLLECTIONS

JAVASCRIPT

var personMap = {
  "10": new Person("Roger", "Moore"),
  "20": new Person("James", "Bond")
};
var names = [];
for (var key in personMap) {
  if (Object.prototype.hasOwnProperty.call(personMap, key)) {
    if (parseInt(key) > 15) {
      names.push(key + " = " + personMap[key].firstName);
    }
  }
}

ECMASCRIPT 6

const personMap = new Map([
  [10, new Person("Roger", "Moore")],
  [20, new Person("James", "Bond")]
]);
const names = [];
for (const [key, person] of personMap) {
  if (key > 15) {
    names.push(`${key} = ${person.firstName}`);
  }
}

TYPESCRIPT

/// <reference path="dts/typescript/lib.es6.d.ts" />

const personMap = new Map<number, Person>([
  [10, new Person("Roger", "Moore")],
  [20, new Person("James", "Bond")]
]);
const names = new Array<string>();
for (const [key, person] of personMap) {
  if (key > 15) {
    names.push(`${key} = ${person.firstName}`);
  }
}

SCALA.JS

val personMap = Map(
  10 -> new Person("Roger", "Moore"),
  20 -> new Person("James", "Bond")
)
val names = for {
  (key, person) <- personMap
  if key > 15
} yield s"$key = ${person.firstName}"

To find out more about what Scala.js looks like for JavaScript developers, check
out the detailed comparisons. If you want to try it out yourself, check out the
Tutorials!

Feature JavaScript ES5 JavaScript ES6 TypeScript Scala.js Interoperability Fully
EcmaScript5 compatible No compilation required Use existing JS libraries
Language features Classes Modules Support for types Strong type system Extensive
standard libraries Optimizing compiler Macros, to extend the language IDE
support Catch most errors in IDE Easy and reliable refactoring Reliable code
completion

LEARN


Documentation
Tutorial


COMMUNITY


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