Search code examples
javascriptcomputed-properties

computed property names and this - JS


Can i use this in computed property name ? something like this:

class User {
  constructor(username) {
    this._username = username;
  }

  [this._username + "Print"]() {
    console.log(this._username);
  }
}

const u = new User("MORA");
u.moraPrint(); // ?

And i know that it is useless in this case.


Solution

  • If you define your function in your constructor, it can be done:

    class User {
      constructor(username) {
        this._username = username;
        this[username + "Print"] = function () {
        console.log(this._username);
        
        }
      }
    }
    
    
    
    const u = new User("mora");
    u.moraPrint(); // ?

    A class function can be created with computed property name, but as mentioned in comment this would not have been initialized by then, because there is no object instance.

    You can check that by running this (pun intended) code :

    item = 'hey'
    class User {
      constructor(username) {
        this._username = username;
      }
    
      [this.item + "hello"]() {
        console.log('hello ' + this._username);
      }
    }
    
    const u = new User("MORA");
    u.heyhello(); // ?

    The value of this is different because at the time code is run, the context is different.