JavaScript: this

JavaScript this refers to a value chosen by the way a function is called.

Method context

const user = {
  name: "Aki",
  greet() {
    console.log(this.name);
  }
};

user.greet(); // Aki

When JavaScript evaluates user.greet(), this inside greet refers to user. Calling the same function without its object can produce a different value.

Other common contexts

• Inside a constructor called with new, this is the new instance.
• In an arrow function, this is taken from the surrounding scope; the arrow does not create its own value.
• In a strict-mode ordinary function called by itself, this is undefined.
• In a browser event handler registered as a normal function, this commonly refers to the element receiving the event.

Common mistake

Do not decide what this means from where a function is written. First inspect how it is called, then check whether it is an arrow function, a method, or a constructor.