deno.md

Deno Online Compiler

Write, Run & Share Deno code online using OneCompiler's Deno online compiler for free. It's a modern, secure, and feature-rich runtime for JavaScript and TypeScript. Getting started with OneCompiler's Deno editor is easy and fast. The editor shows sample boilerplate code when you choose Deno as the language and start coding.

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About Deno

Deno is a secure runtime for JavaScript and TypeScript, built on V8 and Rust. It is designed by the creator of Node.js to improve upon its shortcomings, offering modern features with better security and developer experience.

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Key Features

• Secure by default: No file, network, or environment access unless explicitly granted.
• Built-in TypeScript support: No need for a separate compiler.
• Uses modern ES modules: No need for package.json or node_modules.
• Ships with a built-in formatter, linter, and test runner.
• Supports Web APIs: Similar to browsers, Deno includes APIs like fetch().

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Syntax Help

Hello World

console.log("Hello, World!");

Variable Declaration

Keyword	Description	Scope
var	Old way of declaring variables	Function or global
let	Block-scoped variable	Block scope
const	Constant, cannot be reassigned	Block scope

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Arrow Functions

Arrow functions provide a more concise syntax for defining functions.

Syntax:

const greet = (name: string): string => `Hello, ${name}!`;
console.log(greet("Deno"));

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Template Literals (Backtick Strings)

Interpolation

let name = "Deno";
console.log(`Hello, ${name}!`);

Multi-line Strings

const message = `
Hello,
Welcome to Deno!
`;
console.log(message);

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Arrays

An array is a collection of values.

Syntax:

let numbers: number[] = [1, 2, 3, 4, 5];
console.log(numbers[0]); // Accessing first element

Spread operator with Arrays

let moreNumbers = [...numbers, 6, 7, 8];
console.log(moreNumbers);

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Object Destructuring

Example:

const user = { name: "Alice", age: 25 };
const { name, age } = user;
console.log(name, age);

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Loops

For Loop

for (let i = 0; i < 5; i++) {
  console.log(i);
}

While Loop

let count = 0;
while (count < 5) {
  console.log(count);
  count++;
}

Do-While Loop

let num = 0;
do {
  console.log(num);
  num++;
} while (num < 5);

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Classes

Deno supports ES6 classes, allowing for object-oriented programming.

Example:

class Car {
  model: string;
  constructor(model: string) {
    this.model = model;
  }
  showModel() {
    console.log(`Car model: ${this.model}`);
  }
}

const myCar = new Car("Tesla Model S");
myCar.showModel();

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Deno is a modern and secure alternative to Node.js, offering built-in TypeScript support and a more streamlined developer experience. With its security-first approach and native ES module support, it is a great choice for modern JavaScript and TypeScript applications.