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Advanced JavaScript Fundamentals

6. ES6 Classes

Lesson 6 instructor notes)

  • Sugar over functions and the prototype chain
  • While ES6 Classes arae syntactic sugar, they also also have their own things that only exist with classes. -Classes are not hoisted, unlike functions which are. -Has many keywords specific to ‘class’, but it is still just sugar.

‘extends’

  • Subclasses custom classes and built-in objects.

  • Equivalent of using Object.setPrototypeOf with two functions before new keyword. Example:

class Square extends Rectangle {}

Object.getPrototypeOf(Square) // class Rectangle {}

Constructor

  • Special method on a class. It is what is called when you new up a class.
  • One constructor per class.

Static

  • Used to set the property to the class itself.
  • Will not go onto the .prototype property
  • Should not be called on instances of class

Super keyword

Super is a way of accessing methods whether static or constructor.. super gives us access to anything on the parent class. Your child class has to call ‘super’ before it uses ‘this.`

The new keyword goes through classes on extends and looks at constructors. To complete the chain, super is required in children constructors. Must call super on child classes.

Additional notes/resources:

  • Things have been built around ES6 classes to make classes work like how they would in classical languages.

  • When we create classes in react we are extending react.component. It was a child class of another class and it had a constructor, which means we need to use Super.