Javascript classes define attribute in constructor or outside the class

Question

I am creating a project that defines the following class:

class BankAccount {
 constructor(balance=0){
   this.balance = balance;
 }

 withdraw(amount){
    if(this.balance - amount >= BankAccount.overdraftlimit){
      this.balance -= amount;
    }
  }
}

BankAccount.overdraftlimit = -500;

My question here is about the definition of the property overdraftlimit

Is this the best way to define let's call a global property? Or should be better to define it inside the constructor like

this.overdraftlimit = -500;

Thank you!!

that depends on your domain. can different bank account have different overdraftlimit? should a bank account be able to mutate it? — Federkun
– Federkun, Commented Aug 17, 2019 at 1:19
thanks for responding. No, another bank account cannot mutate it, and there will be different bank accounts with different overdraftlimits — Ruben Saucedo
– Ruben Saucedo, Commented Aug 17, 2019 at 1:21
if the overdraftlimit is not part of any specific instance, then it make sense to be defined as part of the class itself. otherwise make that part of your instance state. — Federkun
– Federkun, Commented Aug 17, 2019 at 1:22
I personaly would set this property in the constructor with a default value and create setter and getter for it — user11146000
– user11146000, Commented Aug 17, 2019 at 1:24
ok, so I understand that if it is defined as part of the class is independant of the instance and any instance can not mutate it. — Ruben Saucedo
– Ruben Saucedo, Commented Aug 17, 2019 at 1:25

Federkun · Accepted Answer · 2019-08-17 01:35:40Z

3

If the overdraftlimit is shared across all the BankAccount, then go with the static propriety.

BankAccount.overdraftlimit = -500;

If every BankAccount have their own overdraftlimit, it should not be part of the class, but part of the single instances.

 constructor(balance = 0){
   this.balance = balance;
   this.overdraftlimit = -500;
 }

this way you could also change overdraftlimit without affecting other BankAccount.

answered Aug 17, 2019 at 1:35

Federkun

37.1k8 gold badges82 silver badges93 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Ruben Saucedo Over a year ago

ohhh, ok I got it. Declare it as a static property makes that this property can be shared by all the instances. If one change it, it will affect the other instances. As you was saying part of the class not of the instance. That is what you mean right? Great explanation

Federkun Over a year ago

yeah, that's it

Collectives™ on Stack Overflow

Javascript classes define attribute in constructor or outside the class

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related