In JavaScript, is constructor mandatory in a class?

You should just write a class without a constructor and see if it works :)

From the same docs

As stated, if you do not specify a constructor method a default constructor is used. For base classes the default constructor is:

constructor() {}

For derived classes, the default constructor is:

constructor(...args) {
  super(...args);
}

No, It is not necessary. By default constructor is defined as :

constructor() {}

For inheritance we use this constructor to call super class as :

constructor() {
    super.call()
}

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