The this keyword is perhaps one of the most rage-inducing parts of JavaScript. Once you understand it, it's not too bad, but it's far from intuitive (in my opinion).
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Put simply, this refers to the context where a piece of code is executed... let's cover some of those cases:
this refers to the window object in browsers or module.exports in Node.js (not global, as you might expect).
// in a browser
console.log(this);
// Window { ... }
// in Node.js
console.log(this);
// {}
In strict mode (which we'll cover later, don't worry about it too much for now) this is undefined in the global scope in both the browser and Node.js.
"use strict";
console.log(typeof this);
// undefined
Inside a standard method or a constructor, this refers to the object the method is called on.
const myObject = {
message: "Hello, World!",
myMethod() {
console.log(this);
console.log(this.message);
},
};
myObject.myMethod();
// {"message":"Hello, World!"}
// Hello, World!
We'll cover arrow functions specifically in the next lesson - they're a bit of a special case.