第三章 Typescript 基本数据类型

Typescript 基本数据类型

一、基本数据类型

• Boolean
• Number
• String
• Array
• Tuple
• Enum
• Any
• Void
• Null 和 Undefined
• Never

二、代码示例

//布尔值

let isDone: boolean = false;

//数字(可以是二进制、八进制、十六进制)

let decLiteral: number = 6;

let hexLiteral: number = 0xf00d;

let binaryLiteral: number = 0b1010;

let octalLiteral: number = 0o744;

//字符串

let name: string = "bob";

name = "smith";

//使用模版字符串

let name: string = `Gene`;

let age: number = 37;

let sentence: string = `Hello, my name is ${name}.

I'll be ${age + 1} years old next month.`;

//数组

let list: number[] = [1, 2, 3];

//Array<元素类型>

let list: Array<number> = [1, 2, 3];

//元组 Tuple

// Declare a tuple type

let x: [string, number];

// Initialize it

x = ["hello", 10]; // OK

// Initialize it incorrectly

x = [10, "hello"]; // Error

//枚举

enum Color {

    Red,

    Green,

    Blue

}

let c: Color = Color.Green;

enum Color {

    Red = 1,

    Green,

    Blue

}

let c: Color = Color.Green;

enum Color {

    Red = 1,

    Green = 2,

    Blue = 4

}

let c: Color = Color.Green;

enum Color {

    Red = 1,

    Green,

    Blue

}

let colorName: string = Color[2];

alert(colorName); // 显示'Green'因为上面代码里它的值是2

//Any

let notSure: any = 4;

notSure = "maybe a string instead";

notSure = false; // okay, definitely a boolean

//Any数组

let list: any[] = [1, true, "free"];

list[1] = 100;

//Void

function warnUser(): void {

    alert("This is my warning message");

}

let unusable: void = undefined;

//Null 和 Undefined

let u: undefined = undefined;

let n: null = null;

//Never

// 返回never的函数必须存在无法达到的终点

function error(message: string): never {

    throw new Error(message);

}

// 推断的返回值类型为never

function fail() {

    return error("Something failed");

}

// 返回never的函数必须存在无法达到的终点

function infiniteLoop(): never {

    while (true) {}

}

//类型断言

let someValue1: any = "this is a string";

let strLength1: number = (someValue1 as string).length;

let someValue: any = "this is a string";

let strLength: number = (<string>someValue).length;