this-keyword.md

In JavaScript, this is a special keyword that's set when a function is called, and it refers to the context in which the function was called. The value of this is not determined by how a function is defined, but by how it's called.

let obj = {
  name: 'John',
  greet: function() {
    console.log(`Hello, ${this.name}`);
  }
};

obj.greet(); // "Hello, John"

In this example, this inside the greet method refers to obj.

Pros:

• It allows you to access the context in which a function was called.
• It's very useful in "object-oriented programming" (in this case we are talking about prototypal inheritance, where you want methods to have access to their object's properties.

Cons:

• The value of this can be confusing, especially in nested functions or callbacks where it might not be what you expect.
• It can lead to bugs if not understood correctly.

Kyle Simpson, in his "You Don't Know JS" series, has a lot to say about this:

"Instead of relying on this, you could use an object reference to keep the binding to the desired object, making the this style of coding unnecessary. It's a choice of style and readability, not of functionality."

And:

"I think this is cool, but it's also easily one of the most misunderstood mechanisms in JavaScript and is often avoided as such."