Question

我想验证用户表单输入，我只是编写这段代码，但实际上有一个我无法修复的错误，我也不明白为什么它在这里（错误）。

let User = (data) => {
    this.data = data
    this.errors = []
}
User.prototype.validation = () => {
    if(this.data.username == ""){
        this.errors.push("You must* provide a username")
    }else if(this.data.email == ""){
        this.errors.push("You must* provide the email address for you account")
    }else if(this.data.password == ""){
        this.errors.push("You must* provide the password for your account")
    }
}
User.prototype.register = () => {
    // step #1 validate user data
    this.validation()
    // step #2 only if there are no validation errors
    // then save the user data into a database
}

module.exports = User

和我得到的错误。

User.prototype.validation = () => {
                          ^

TypeError: Cannot set property 'validation' of undefined
    at Object.<anonymous> (C:\Users\40sherrin\Desktop\application\models\User.js:5:27)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Module.require (internal/modules/cjs/loader.js:637:17)
    at require (internal/modules/cjs/helpers.js:22:18)
    at Object.<anonymous> (C:\Users\40sherrin\Desktop\application\controllers\userController.js:1:76)
    at Module._compile (internal/modules/cjs/loader.js:689:30)

Answer 1

defining a constructor function不能使用箭头功能。

箭头函数表达式在语法上紧凑于正则函数表达式，尽管没有自己的绑定 this，arguments，super或new.target关键字。 箭头功能表达式不适合用作方法，因此不能用作构造函数。

使用原型属性

箭头功能没有原型属性。

let User = function (data) {
    this.data = data
    this.errors = []
}
User.prototype.validation = function() {
    if(this.data.username == ""){
        this.errors.push("You must* provide a username")
    }else if(this.data.email == ""){
        this.errors.push("You must* provide the email address for you account")
    }else if(this.data.password == ""){
        this.errors.push("You must* provide the password for your account")
    }
}
User.prototype.register = function() {
    // step #1 validate user data
    this.validation()
    // step #2 only if there are no validation errors
    // then save the user data into a database
}

因此，请改用function或ES6类。


class User {

   constructor(data) {
       this.data = data
       this.errors = []
   }

   validation() {
      // ...
   }

   register() {
      this.validation();
   }
}

Answer 2

fat arrow functions do not have prototypes。

JavaScript / NodeJs-TypeError：无法设置未定义的属性“ validation”

2 个答案: