SyntaxError: Unexpected token { when trying to export a class in es5 module for use in another module

Question

知道错误是如何发生的吗？ class 看起来是在 ..

上声明的

car.js

function Car() {}

Car.prototype.setNumberOfWheels(numberOfWheels) {
    this.numberOfWheels = numberOfWheels;
}

Car.prototype.print() {
    console.log(this);
}

module.exports.Car = Car;

server.js

const model = require('./model.js');

错误：

Car.prototype.setNumberOfWheels(numberOfWheels) {
                                                ^

SyntaxError: Unexpected token {
    at createScript (vm.js:80:10)
    at Object.runInThisContext (vm.js:139:10)
    at Module._compile (module.js:617:28)
    at Object.Module._extensions..js (module.js:664:10)
    at Module.load (module.js:566:32)
    at tryModuleLoad (module.js:506:12)
    at Function.Module._load (module.js:498:3)
    at Module.require (module.js:597:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (/Users/bob/git/project/server.js:2:15)

Answer 1

您应该将 setNumberOfWheels 和 print 声明为函数。

Car.prototype.setNumberOfWheels = function(numberOfWheels) {
    this.numberOfWheels = numberOfWheels;
}

Car.prototype.print = function() {
    console.log(this);
}

Answer 2

使用 shorthand syntax（在对象初始值设定项上）声明方法的正确方法是：

var car = {}

然后添加方法，

Car.prototype.setNumberOfWheels = numberOfWheels => {
    this.numberOfWheels = numberOfWheels;
}

Car.prototype.print = () => {
    console.log(this);
}

Answer 3

在 Ecmascript-5 中，您必须将 setNumberOfWheels 和 print 定义为函数 (see prototype examples)

function Car() {}

Car.prototype.setNumberOfWheels = function(numberOfWheels) {
    this.numberOfWheels = numberOfWheels;
}

Car.prototype.print= function() {
    console.log(this);
}

module.exports.Car = Car;

您可以使用ES6 Classes

class Car {
    setNumberOfWheels(numberOfWheels) {
        this.numberOfWheels = numberOfWheels;
    }
    print() {
        console.log(this);
    }
}


module.exports.Car = Car;

SyntaxError: Unexpected token { when trying to export a class in es5 module for use in another module

SyntaxError: Unexpected token { when trying to export a class in es5 module for use in another module

javascript

ecmascript-5