TypeError：无法设置未定义的属性“ validate”

Question

尝试在我的应用上设置验证，但我不知道为什么收到此TypeError

这是用于连接到mongodb的Node js应用程序。我已尝试使用Google搜索，但尚未找到答案。

let User = data => {
  this.data = data;
  this.errors = [];
};

User.prototype.validate = () => {
  if (this.data.username == "") {
    this.errors.push("You must provide a username.");
  }
  if (this.data.email == "") {
    this.errors.push("You must provide a valid email address");
  }
  if (this.data.password == "") {
    this.errors.push("You must provide a password.");
  }
  if (this.data.password.length > 0 && this.data.password.length < 12) {
    this.errors.push("Username must be at least 12 characters.");
  }
  if (this.data.password.length > 100) {
    this.errors.push("Password cannot exceed 100 characters");
  }
  if (this.data.username.length > 0 && this.data.username.length < 3) {
    this.errors.push("Username must be at least 3 characters.");
  }
  if (this.data.username.length > 30) {
    this.errors.push("Password cannot exceed 30 characters");
  }
};

User.prototype.register = () => {
  // Step #1: Validate user data

  this.validate();
};

module.exports = User;

我希望此输出可以验证注册表单