第三章 Typescript 基本数据类型

Posted 2020-10-19 水之原

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;