Typescipt核心概念

Typescript核心

基本类型(Basic Types)

String

var name: string = 'Felipe';

Number

var age: number = 36;

Boolean

var married: boolean = false;

Array

var jobs: Array<string> = ['IBM', 'Microsoft', 'Google'];
var jobs: string[] = ['Apple', 'Dell', 'HP'];
var jobs: Array<number> = [1, 2, 3];
var jobs: number[] = [4, 5, 6];

元组(tuple)

let jobs: [string , number , string];
jobs = ['s1' , 12 , 's2']

Enums

enum Role {Employee, Manager, Admin};
var role: Role = Role.Employee;

Any

var something: any = 'as string';
something = 1;
something = [1, 2, 3];

Void

function setName(name: string): void {
    this.name = name;
}

Null ，Undefined

let u: undefined = undefined;
let n: null = null;

Never

代表从来不会出现的值。

// Function returning never must have unreachable end point
function infiniteLoop(): never {
    while (true) {
    }
}

声明(Variable Declarations)

声明var , let , const ，作用域类似ES6
解构赋值：数组解构，对象解构与ES6类似。

函数(Functions)

function buildName(firstName: string, lastName?: string):string {
    if (lastName)
        return firstName + " " + lastName;
    else
        return firstName;
}


let result1 = buildName("Bob");  // works 
let result2 = buildName("Bob", "Adams", "Sr.");  // error, too many parameters
let result3 = buildName("Bob", "Adams");  // ah, just right
let result3 = buildName(1, 2);  // error

支持默认参数，可选参数，剩余参数，箭头函数等

类(Classes)

修饰符关键字public,private , protected, static ，readonly

class Person {
      static version = '1.0.0';
      protected sexes = ['male' , 'female'];
      first_name: string;
      last_name: string;
      age: number;
      constructor(first_name: string, last_name: string, age: number) {
        this.first_name = first_name;
        this.last_name = last_name;
        this.age = age;
      }
      greet() {
        console.log("Hello", this.first_name);
      }
      ageInYears(years: number): number {
        return this.age + years;
      } 
}

继承和抽象类(Abstract Classes)

abstract class Animal {
    abstract makeSound(): void; //必须在派生类中实现
    move(): void {
        console.log("roaming the earth...");
    }
}

//派生类
class Person extends Animal {
    makeSound():void {
        console.log("say sb");
    }
}

接口(Interfaces)

属性接口

interface FullName {
   firstName: string;
   lastName?: string;
}

function logName(name: FullName) {
    console.log(name.firstName , name.lastName);
}

函数类型接口

interface SearchFunc {
    (source: string, subString: string): boolean;
}
let mySearch: SearchFunc;
mySearch = function(source: string, subString: string) {
    let result = source.search(subString);
    return result > -1;
}

类类型接口

interface ClockInterface {
    currentTime: Date;
}

class Clock implements ClockInterface {
    currentTime: Date;
    constructor(h: number, m: number) { }
}

泛型(Generic)

function identity1(arg: number): number {
    return arg;
}
function identity2(string: string): string {
    return arg;
}
// 放弃类型检查
function identity(arg: any): any {
    return arg;
}
//使用泛型
function identity<T>(arg: T): T {
    return arg;
}
// test ...
let output = identity<string>("myString");  
// or
let output = identity<number>("myString");

模块(Modules)

与es6一样，使用export和import导出导入模块。

装饰器(Decorators)

Typescript提供的几种装饰器:

Alt text

方法装饰器

@enumerable decorator 的定义

function enumerable(value: boolean) {
    return function (
        // 类的原型对象
        target: any, 
        // 方法的名字
        propertyKey: string, 
        // 成员属性的描述
        descriptor: PropertyDescriptor) {
            descriptor.enumerable = value;
        };
}

@enumerable decorator 的使用

class Greeter {
    greeting: string;
    constructor(message: string) {
        this.greeting = message;
    }

    @enumerable(false)
    greet() {
        return "Hello, " + this.greeting;
    }
}

类装饰器：

@Component装饰器

@Component({
  selector: 'app-user-list',
  templateUrl: './user-list.component.html',
  styleUrls: ['./user-list.component.css']
})
export class UserListComponent implements OnInit {
  names: string[];
  constructor() {
    this.names = ['Ari', 'Carlos', 'Felipe', 'Nate'];
  }
  ngOnInit() {
      console.log('com init hook')
  }
}

参数装饰器：

class Greeter {
    greeting: string;

    constructor(message: string) {
        this.greeting = message;
    }
    
    greet(@required name: string) {
        return "Hello " + name + ", " + this.greeting;
    }
}

属性装饰器：

class Greeter {
    @format("Hello, %s")
    greeting: string;

    constructor(message: string) {
        this.greeting = message;
    }
    greet() {
        let formatString = getFormat(this, "greeting");
        return formatString.replace("%s", this.greeting);
    }
}

装饰器组合：

@decorator1
@decorator2
class Person(){}

ES2017 已经引入了这项功能，目前 Babel 转码器已经支持。

Typescript提供的几种装饰器源码

其他

Symbols 、迭代器、命名空间(namespace)等

小结