Play with Coding — Learn to code. Play to grow.

Everything in one place

Use this chapter as a quick reference once you've worked through the rest of the course. It collects every core construct of TypeScript into runnable, copy-pasteable snippets you can scan whenever you forget the exact syntax.

Hello world & variables

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

let age: number = 25; const name: string = "Aman"; let isStudent: boolean = true; ```

Data types & operators

```typescript
let n: number = 42;
let s: string = "hello";
let b: boolean = true;
let arr: number[] = [1, 2, 3];
let maybe: string | null = null;

const a = 10, b = 3; console.log(a + b, a % b); console.log(a > b && b < 5); ```

Conditionals & loops

```typescript
const score: number = 72;
if (score >= 90) console.log("A");
else if (score >= 60) console.log("Pass");
else console.log("Fail");

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

const items: string[] = ["a", "b"]; for (const x of items) console.log(x); ```

Functions & arrays

```typescript
function add(a: number, b: number): number {
  return a + b;
}
const square = (x: number) => x * x;

const nums: number[] = [10, 20, 30]; const doubled = nums.map((n) => n * 2); const sum = nums.reduce((t, n) => t + n, 0); ```

Strings & objects

```typescript
const name = "PlayLearn";
console.log(name.length);
console.log(name.toUpperCase());
const greet = `Hello, ${name}!`;

interface User { name: string; age: number; } const u: User = { name: "Aman", age: 20 }; console.log(u.name); ```

Errors, modules & I/O

```typescript
try {
  JSON.parse("not json");
} catch (err: unknown) {
  if (err instanceof Error) console.error(err.message);
}

// math.ts export function add(a: number, b: number): number { return a + b; }

// main.ts import { add } from "./math"; console.log(add(2, 3));

import fs from "node:fs/promises"; const text: string = await fs.readFile("notes.txt", "utf8"); console.log(text); ```

How to use this page

Bookmark it. When you start a new project, open this cheatsheet alongside your editor and use it as a syntax lookup. Once a construct becomes second nature you'll stop needing the reference for it — and that's exactly when you know you've mastered that part of TypeScript.

TypeScript Syntax Cheatsheet