程式印象: y分學typescript

2019年11月19日星期二

y分學typescript

為什麽學

它能讓專案更加可靠，像一般用Javascript寫程式不宣告型別很方便，少打幾個字。可是遇到要用這個變數時，會疑惑著個變數究竟是什麽型別，型別不知道誤用函數，就會造成很多不必要的錯誤。

用typescript強型別的語言，強型別就是使用變數前必須宣告型別的意思，用這個語言能減少變數型別的問題。

步驟

下載安裝Node.js。
安裝typescript指令 npm install -g typescript。
建立檔案first-typescript.ts。
寫程式。
編譯.ts 檔案為 .js 指令 tsc first-typescript.ts。

first-typescript.ts程式碼

	//1.Install typescript
	// npm install -g typescript
	//2.Create a file first-typescript.ts
	//3.Coding
	//4.Compile .ts file to .js file.
	// tsc first-typescript.ts
	let a = 5;
	let b = 5;
	let c = a + b;
	console.log(c);

	let myVariable: any = 'This is a string'
	console.log('any type:'+myVariable);

	let num: number = 5;
	let name1: string = 'Alex';
	let isPresent: boolean = true;
	let num1: void;
	let name_a: undefined;
	let isPresent1:null;
	console.log('built-in types:'+name1);

	let numbers: Array<number> = [0, 1, 2, 3, 4];
	let moreNumbers: ReadonlyArray<number> = numbers;
	//moreNumbers[5] = 5; // Error, elements are read-only
	enum Color { Red, Green, Blue };
	let color: Color = Color.Green;
	console.log('user-defined types');

	class Car {

	// fields
	model: String;
	doors: Number;
	isElectric: Boolean;

	constructor(model: String, doors: Number, isElectric: Boolean) {
	this.model = model;
	this.doors = doors;
	this.isElectric = isElectric;
	}

	displayMake(): void {
	console.log(`This car is ${this.model}`);
	}

	}
	const Prius = new Car('Prius', 4, true);
	Prius.displayMake(); // This car is Prius
	console.log('class test');

	interface ICar {
	model: String,
	make: String,
	display(): void
	}

	const UberCar: ICar = {
	model: 'Prius',
	make: 'Toyota',
	display():void { console.log('hi'); }
	}
	console.log('use interface to define the structure of variables.');

	// Generics
	// Classes
	class Tuple<T1, T2> {
	constructor(public item1: T1, public item2: T2) {
	}
	}

	// Interfaces
	interface Pair<T> {
	item1: T;
	item2: T;
	}

	// And functions
	let pairToTuple = function <T>(p: Pair<T>) {
	return new Tuple(p.item1, p.item2);
	};

	let tuple = pairToTuple({ item1: "hello", item2: "world" });
	console.log('tuple example');