Is basically telling what type something is.
For example let say we have a box,
and we want to tell people to only put eggs in the box.
let myBox; // 📦 In real life we would put a sticker in the box saying "only eggs
please 📄", in TypeScript we do the same, we add a "type" saying what something is and only accepts.
Variable Type value ┌────┴─────┐ ┌────┴─────┐ ┌───┴───┐ let myBox_📦 : onlyEggs_📄 = "🥚🥚🥚"; ↑ ↑ Separator Assignment operator There are 3 basic types in TypeScript
let isDone: boolean = false; // 😀 or 😟 let lines: number = 42; // 0️⃣1️⃣2️⃣3️⃣4️⃣5️⃣... let name: string = "John"; // 📃 When it's impossible to know, there is the "Any" type
let notSure: any = 4; // 🤷♂️ Not sure notSure = "I'm a string"; // I can change it later notSure = false; // maybe a boolean There are typed arrays
let list: number[] = [1, 2, 3]; // or with emojis: Only chickens please! ┌─┴─┐ let chickens: 🐔[] = [🐣,🐤,🐥,🐓]; Alternatively you can use Array which It's same as Type[]
let list: Array<number> = [1, 2, 3]; // or with emojis let listOfChickens: Array<🐔> = [🐣,🐤,🐥,🐓]; Enumerations also known as enums:
enum Square { Red, Green, Blue }; // 🟥, 🟩, 🟦 // This can be understood better by seeing what Enumerations // are compiled to in JavaScript: Square = { 0 : 'Red', 1 : 'Green', 2 : 'Blue', Red : 0, Green : 1, Blue : 2, }; // Now that you know is just an object, // you can access it by name or number. console.log( Square.Green ); // 🟩 console.log( Square[2] ); // 🟥 // or in a more complex way let c: Square = Square.Blue; console.log( Square[c] ); // 🟦 Please Comment if you want to see more content like this!
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