TypeScript: The Key to Building High-Performance JavaScript Applications — From Angular to React, Node to Web Workers, and More
TypeScript is a programming language that is a strict syntactical superset of JavaScript. It adds optional static typing, classes, and interfaces to JavaScript, and is designed for large-scale JavaScript applications. It was developed and is maintained by Microsoft.
TypeScript code is transpiled into JavaScript code, which can then run in any JavaScript environment. This means that TypeScript can be used in any project that uses JavaScript, but it also means that you can use all the features of JavaScript in TypeScript.
Here are some basic code samples of TypeScript:
Variables: TypeScript supports the same variable types as JavaScript (number, string, boolean, etc.), but it also allows you to specify the type of a variable:
let myNumber: number = 5;
let myString: string = "Hello, TypeScript";
let myBoolean: boolean = true;Classes: TypeScript supports classes, which are a way to define object-oriented classes in JavaScript:
class MyClass {
myNumber: number;
constructor(num: number) {
this.myNumber = num;
}
printNumber() {
console.log(this.myNumber);
}
}
let myObj = new MyClass(5);
myObj.printNumber(); // prints "5"Interfaces: TypeScript supports interfaces, which are a way to describe the shape of an object:
interface MyInterface {
myNumber: number;
myString: string;
}
let myObj: MyInterface = {
myNumber: 5,
myString: "Hello, TypeScript"
};
console.log(myObj.myNumber); // prints "5"
console.log(myObj.myString); // prints "Hello, TypeScript"TypeScript also provides a lot of advanced features such as Generics, Decorators, Modules etc. With TypeScript you can write better, more maintainable code and catch errors at compile-time rather than at runtime. It also makes it easier to work on large-scale projects, by providing better support for refactoring and code navigation.
Function Types: TypeScript allows you to specify the types of function parameters and return values.
function add(a: number, b: number): number {
return a + b;
}
let result = add(1, 2); // valid
let result = add("1", 2); // Invalid, since the function expects numbers as argumentsEnums: TypeScript supports enums, which is a way to define a set of named constants.
enum Colors {
Red,
Green,
Blue
}
let myColor: Colors = Colors.Green;
console.log(myColor); // prints "1"Type Inference: TypeScript can infer the type of a variable from the value assigned to it, which means you don’t always have to explicitly specify the type.
let myNumber = 5; // TypeScript infers that this variable is of type "number"
let myString = "Hello, TypeScript"; // TypeScript infers that this variable is of type "string"Union Types: TypeScript allows you to specify a variable that can have one of several types.
let myValue: number | string;
myValue = 5; // valid
myValue = "hello"; // valid
myValue = true; // InvalidIt is important to note that TypeScript is a superset of JavaScript, so all valid JavaScript code is also valid TypeScript code. However, TypeScript can catch errors that would otherwise only be detected at runtime, which makes it a powerful tool for building large-scale JavaScript applications.
In Angular, TypeScript is used as the primary language for building Angular Applications. Angular makes use of the features of TypeScript such as classes, interfaces, and decorators to provide a powerful and expressive syntax for building web applications.
Generics: TypeScript provides the ability to create reusable components using Generics. Generics are a way to create a component that can work with multiple types.
function identity<T>(arg: T): T {
return arg;
}
let output = identity<string>("myString"); // type of output will be 'string'
let output = identity<number>(1); // type of output will be 'number'Decorators: TypeScript allows you to use decorators, which are a way to add meta-data to a class, property, method or parameter.
function Logger(target: any, propertyKey: string | symbol) {
console.log(`Logger applied to ${propertyKey}`);
}
class MyClass {
@Logger
myMethod() {}
}Modules: TypeScript has a way to organize the code in your application in to self-contained units called modules.
export class MyClass {
// class implementation
}
import {MyClass} from "./myclass";
let obj = new MyClass();Linting: TypeScript provides a way to enforce coding conventions and improve the code quality by using linting tools such as TSLint. This is done by configuring a set of rules that the linter will check the code against.
// tslint.json
{
"rules": {
"no-var-keyword": true,
"object-literal-sort-keys": true
}
}By using these features of TypeScript, you can write more maintainable, reliable, and scalable code for your JavaScript application. TypeScript is not only useful for Angular, but it can be used in any JavaScript project.
TypeScript and React: TypeScript can also be used in React applications. React has official support for TypeScript and you can use it by adding TypeScript and the @types/react package to your project. You can use TypeScript to define the types of your components’ props and state, and also use interfaces and type aliases to define the shape of your data.
interface Props {
name: string;
age: number;
}
class MyComponent extends React.Component<Props> {
render() {
return <div>{this.props.name}</div>;
}
}TypeScript and Node.js: TypeScript can also be used to build backend applications with Node.js. Node.js has official support for TypeScript and you can use it by adding TypeScript and the @types/node package to your project. You can use TypeScript to define the types of your modules, functions, and variables, and also use interfaces and type aliases to define the shape of your data.
import express from "express";
const app = express();
app.get("/", (req, res) => {
res.send("Hello World!");
});
app.listen(3000, () => {
console.log("Example app listening on port 3000!");
});TypeScript and Vue.js: TypeScript can also be used in Vue.js applications. Vue has official support for TypeScript and you can use it by adding the @vue/cli-plugin-typescript package to your project. You can use TypeScript to define the types of your Vue components’ props, data, and computed properties, and also use interfaces and type aliases to define the shape of your data.
<template>
<div>
{{ message }}
</div>
</template>
<script lang="ts">
import { Component, Prop, Vue } from "vue-property-decorator";
@Component
export default class MyComponent extends Vue {
@Prop() private message!: string;
}
</script>By using TypeScript in your application, you can catch errors at compile-time, write more maintainable and scalable code, and take advantage of all the features that TypeScript provides.
It’s important to note that you can use TypeScript with other JavaScript libraries, frameworks and even in a simple Node.js or browser project, TypeScript is not limited to Angular and it’s a versatile language.
TypeScript and Webpack: TypeScript can also be used in combination with webpack, which is a popular JavaScript bundler. You can set up a TypeScript project with webpack by installing the necessary loaders and plugins, and configuring your webpack.config.js file.
module.exports = {
mode: 'development',
entry: './src/index.ts',
output: {
filename: 'bundle.js',
path: path.resolve(__dirname, 'dist'),
},
module: {
rules: [
{
test: /\.tsx?$/,
use: 'ts-loader',
exclude: /node_modules/,
},
],
},
resolve: {
extensions: [ '.tsx', '.ts', '.js' ],
},
};TypeScript and other JavaScript tools: TypeScript can also be used in combination with other JavaScript tools such as Babel, which is a JavaScript compiler, and Jest, which is a JavaScript testing framework. You can set up a TypeScript project with these tools by installing the necessary plugins and configuring your project accordingly.
// babel.config.js
module.exports = {
presets: [
'@babel/preset-typescript',
],
};// jest.config.js
module.exports = {
preset: 'ts-jest',
testEnvironment: 'node',
};TypeScript and Web Components: TypeScript can also be used to build web components, which are a set of technologies that allow you to create reusable custom elements with their own behavior and styles. You can use TypeScript to define the types of your web component’s properties, methods, and events, and also use interfaces and type aliases to define the shape of your data.
class MyElement extends HTMLElement {
private myValue: string;
constructor() {
super();
this.myValue = "Hello, TypeScript";
}
connectedCallback() {
this.innerHTML = `<p>${this.myValue}</p>`;
}
}
customElements.define("my-element", MyElement);TypeScript and GraphQL: TypeScript can also be used in combination with GraphQL, which is a query language for APIs. You can use TypeScript to define the types of your GraphQL schema, and also use interfaces and type aliases to define the shape of your data.
import { gql } from "apollo-server-express";
const typeDefs = gql`
type Query {
user(id: ID!): User
}
type User {
id: ID!
name: String!
age: Int!
}
`;TypeScript and WebSockets: TypeScript can also be used in combination with WebSockets, which is a protocol for real-time communication. You can use TypeScript to define the types of your WebSocket messages and events, and also use interfaces and type aliases to define the shape of your data.
const socket = new WebSocket('ws://localhost:8080');
socket.onmessage = (event: MessageEvent) => {
console.log(event.data);
};
socket.onopen = (event: Event) => {
socket.send('Hello Server!');
};In short, TypeScript is a versatile and powerful language that can be used in a wide range of JavaScript projects. It provides a static type system and other advanced features, which can help you to write more maintainable, reliable, and scalable code. It can be used with a wide range of libraries, frameworks, and tools, and it’s not limited to Angular. It’s important to note that TypeScript can help you to catch errors at compile-time, which reduces the number of runtime errors, and makes your application more robust.
