call, apply & bind

In JavaScript, call, apply, and bind are methods used to explicitly set the this context of a function. This is crucial when you want to control what this refers to inside a function, especially when borrowing methods or working with callbacks.

call()

Calls a function with a specified this context and arguments passed individually.

function greet(greeting, punctuation) {
  console.log(greeting + ', ' + this.name + punctuation);
}

const person = { name: 'Alice' };
greet.call(person, 'Hello', '!'); // Hello, Alice!

apply()

Similar to call, but arguments are passed as an array.

greet.apply(person, ['Hi', '...']); // Hi, Alice...

bind()

Returns a new function permanently bound to a specified this context and optionally preset arguments. It does not call the function immediately.

const greetAlice = greet.bind(person, 'Hey');
greetAlice('!!'); // Hey, Alice!!