no-this-before-super.md

Pattern: Use of this before super() call

Issue: -

Description

In derived class constructors, super() must be called before accessing this or super. Accessing this before super() is called will throw a reference error as the object is not yet initialized.

Examples

Example of incorrect code:

class Animal extends Living {
  constructor() {
    this.legs = 4;  // ReferenceError
    super();
  }
}

class Dog extends Animal {
  constructor() {
    this.bark();  // ReferenceError
    super();
    this.legs = 4;
  }
}

Example of correct code:

class Animal extends Living {
  constructor() {
    super();
    this.legs = 4;  // Valid after super()
  }
}

class Dog extends Animal {
  constructor() {
    super();
    this.bark();  // Valid after super()
    this.legs = 4;
  }
}