导出代码块而不只是功能

Question

Currently in my code, I have VehicleFactory I want to unit test. And VehicleFactory 's prototype is assigned after the declaration of the function:

    export function VehicleFactory() {

    }

    VehicleFactory.prototype.vehicleClass = Car;

    VehicleFactory.prototype.createNewVehicle = function(options) {
        if( options.vehicleType === 'Car') {
            this.vehicleClass = Car;
        }
        else if( options.vehicleType === 'Truck') {
            this.vehicleClass = Truck;
        }

        return new this.vehicleClass(options);
    }

    var factory = new VehicleFactory();
    var car = factory.createNewVehicle( {
        vehicleType: "car",
        color: "yellow",
        doors: 6 } );

function Car(options) {
    if( options.brand != undefined)
        this.brand = options.brand;
    else
        this.brand = "Jeep";

    if( options.color != undefined)
        this.color = options.color;
    else
        this.color = "White";
}

function Truck(options) {
    /// ...
}


    console.log(car);

In my jest:

import VehicleFactory from '../VehicleFactory'
test('vehicleFactory_withCarOptions_AlwaysReturnsCar', () => {
  var factory = new VehicleFactory();
  var car = factory.createNewVehicle( {
    vehicleType: "car",
    color: "yellow",
    doors: 6 } );
  expect(car).toEqual({color: "yellow",
  doors: 6});
});

The error shows:

TypeError: _VehicleFactory.default is not a constructor

  20 |
  21 | test('vehicleFactory_withCarOptions_AlwaysReturnsCar', () => {
> 22 |   var factory = new VehicleFactory();
     |                 ^
  23 |   var car = factory.createNewVehicle( {
  24 |     vehicleType: "car",
  25 |     color: "yellow",

My guess is export only exports the empty function but not the following assignment to prototype? How to fix it?

Answer 1

The problem is I forgot the bracket in import

Instead of import VehicleFactory from '../VehicleFactory' ,

it should be import {VehicleFactory} from '../VehicleFactory'

for named export, I should use bracket,

for default export, I don't need bracket, since one module only has one default export.