从类的构造函数中的另一个属性引用一个属性的值

debugcn 发表于 Dev

阿德巴约

我试图从
构造函数中另一个属性中的另一个方法引用一个属性中前一个方法中返回的值，但我收到“类型错误：无法读取未定义的属性‘名称’”

class Loans {
  constructor(user, loanAmount, tenor, id = 0, status = 'pending', repaid = 'false') {
    this.id = id + 1;
    this.user = user;
    this.loanAmount = loanAmount;
    this.tenor = tenor;
    this.status = status;
    this.repaid = repaid;
    this.interest = (function interest() {
      return (loanAmount * 0.05);
    }());
    this.monthlyInstall = (function monthlyInstall() {
      return (loanAmount + this.interest) / tenor;
    }());
    this.balance = (function balance() {
      return (loanAmount + interest);
    }());
    this.createdAt = new Date().toLocaleString();
  };

};
const loan = new Loans('steve.jobs', 50000, 5);
console.log(loan);

but I got an error ->

      return (loanAmount + this.interest) / tenor;
                                ^

TypeError: Cannot read property 'interest' of undefined
    at monthlyInstall (C:\Users\DEBAYO\Desktop\JavaScript\Challenges\testing.js:183:33)
    at new Loans (C:\Users\DEBAYO\Desktop\JavaScript\Challenges\testing.js:184:6)

德克兹

如果您希望这个数量是动态的（您更新一个值，它们会相应地更新）它们需要是函数。我让他们在下面定义了函数。这意味着如果您更改计算变量之一，它们将自动更新。

class Loans {
  constructor(user, loanAmount, tenor, id = 0, status = 'pending', repaid = 'false') {
    this.id = id + 1;
    this.user = user;
    this.loanAmount = loanAmount;
    this.tenor = tenor;
    this.status = status;
    this.repaid = repaid;
    this.createdAt = new Date().toLocaleString();
  };
  
  interest = () => (this.loanAmount * 0.05);
  monthlyInstall = () => (this.loanAmount + this.interest()) / this.tenor;
  balance = () => (this.loanAmount + this.interest());
};
const loan = new Loans('steve.jobs', 50000, 5);
console.log(loan);
console.log(loan.interest());
console.log(loan.monthlyInstall());
console.log(loan.balance());
loan.tenor = 6;
console.log(loan);
console.log(loan.interest());
console.log(loan.monthlyInstall());
console.log(loan.balance());

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