ts—interscetion Type

& 多个类型集合的交集

| 多个类型集合的并集

使用type定义

type Admin = {
  name: string;
  privileges: string[];
}

type Employee = {
  name: string;
  startDate: Date;
}

type ElevatedEmployee = Admin & Employee;

使用interface定义

interface Admin {
  name: string;
  privileges: string[];
}

interface Employee {
  name: string;
  startDate: Date;
}

interface  ElevatedEmployee extends Admin, Employee{}

使用定义的类型

let ee: ElevatedEmployee = {
  name:'max',
  privileges:['create-admin'],
  startDate:new Date()
}

编译后的js

let ee = {
    name: 'max',
    privileges: ['create-admin'],
    startDate: new Date()
};

使用type 定义任意类型

type Combinable = string | number;

typeGuard: 保护代码在运行时不报错

function printEmployeeInformation(emp: ElevatedEmployee) {
  console.log('name'+ emp.name)
  //判断属性是否存在
  if('privileges' in emp){
    console.log('employee '+ emp.privileges)
  }
  if('startDate' in emp){
    console.log('startDate '+ emp.startDate)
  }
}
printEmployeeInformation(ee)

检验对象的某个属性是否存在
https://dmitripavlutin.com/check-if-object-has-property-javascript/

// @errors: 2493
class Car {
  driver(){
    console.log('driving...')
  }
}

class Truck{
  driver(){
    console.log('driving is truck')
  }

  loadCargo(amount: number){
    console.log('loading cargo' + amount)
  }
}

type Vehicle = Car | Truck;
const v1 = new Car();
const v2 = new Truck();
function useVehicle(vehicle: Vehicle) {
  vehicle.driver();
  if(vehicle instanceof Truck){
    vehicle.loadCargo(1000)
  }
  // if('loadCargo' in vehicle){
  //  vehicle.loadCargo(1000)
  // } 
}
useVehicle(v1);
useVehicle(v2);

//output
// [LOG]: "driving..." 
// [LOG]: "driving is truck" 
// [LOG]: "loading cargo1000"