This content originally appeared on DEV Community and was authored by Mayank Kumar
This ?
The this keyword can lead to some headaches in JavaScript - this blog hopefully acts as a remedy.
this refers to different things, depending on where it's used and how (if used in a function) a function is called !
Generally, this refers to the "thing" which called a function. That can be the global context, an object or some bound data/ object (e.g. when the browser binds this to the button that triggered a click event).
1) this in Global Context (i.e. outside of any function)
function something() { ... }
console.log(this);
// logs global object (window in browser) - ALWAYS (also in strict mode)! ?
2) this in a Function (non-Arrow) - Called in the global context
function something() {
console.log(this);
}
something();
// logs global object (window in browser) in non-strict mode, undefined in strict mode ?
3) this in an Arrow-Function - Called in the global context
const something = () => {
console.log(this);
}
something();
// logs global object (window in browser) - ALWAYS (also in strict mode)! ?
4) this in a Method (non-Arrow) - Called on an object
const person = {
name: 'Mayank',
greet: function() { // or use method shorthand: greet() { ... }
console.log(this.name);
}
};
person.greet();
// logs 'Max', "this" refers to the person object ?
5) this in a Method (Arrow Function) - Called on an object
const person = {
name: 'Max',
greet: () => {
console.log(this.name);
}
};
person.greet();
// logs nothing (or some global name on window object), "this" refers to global (window) object, even in strict mode ?
If in doubt, a console.log(this); can always help you find out what this is referring to at the moment!
HAPPY CODING ??
This content originally appeared on DEV Community and was authored by Mayank Kumar
Mayank Kumar | Sciencx (2021-08-31T07:09:16+00:00) What is ‘this’ ? ?. Retrieved from https://www.scien.cx/2021/08/31/what-is-this-%f0%9f%98%b3/
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