从类的构造函数中的另一个属性引用一个属性的值

Question

I am trying to reference the value returned in a previous method in a property from another method in another property
within the constructor but I get a "TypeError: Cannot read property 'name' of undefined"

 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)

Answer 1

If you want this amount to be dynamic (you update a value they update accordingly) they need to be functions. I made them defined functions below. This means that if you change one of the calculating variables they will be updated automatically.

 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()); 

Answer 2

instead of

this.monthlyInstall = (function monthlyInstall() {
      return (loanAmount + this.interest) / tenor;
    }());

just do

 this.monthlyInstall = (loanAmount + this.interest) / tenor;

Or you need to pass "this" reference into your monthlyInstall() -method, because otherwise it does not know what "this" is.