What is call, apply and bind in JavaScript?

In JavaScript, call, apply, and bind are methods that allow you to invoke a function with a specified this value and arguments.

call method: The call method allows you to invoke a function and specify the this value for the function. The call method takes two or more arguments. The first argument is the value you want to use as the this value, and the rest of the arguments are passed to the function as individual parameters.

let person = {
  name: 'John Doe',
  greet: function(prefix) {
    console.log(prefix + ' ' + this.name);
  }
};

let friend = { name: 'Jane Doe' };

person.greet.call(friend, 'Hello'); // logs 'Hello Jane Doe'

apply method: The apply method is similar to the call method, but it takes an array of arguments instead of individual parameters. The first argument is still the value you want to use as the this value.

let person = {
  name: 'John Doe',
  greet: function(prefix) {
    console.log(prefix + ' ' + this.name);
  }
};

let friend = { name: 'Jane Doe' };

person.greet.apply(friend, ['Hello']); // logs 'Hello Jane Doe'

bind method: The bind method creates a new function with a specified this value and arguments, and returns the new function. When the new function is invoked, it will use the this value and arguments that were specified in the bind method.

let person = {
  name: 'John Doe',
  greet: function(prefix) {
    console.log(prefix + ' ' + this.name);
  }
};

let friend = { name: 'Jane Doe' };

let greetFriend = person.greet.bind(friend, 'Hello');
greetFriend(); // logs 'Hello Jane Doe'

In summary, call, apply, and bind are useful for controlling the this value of a function, and for passing arguments to a function. The main difference between these methods is the way they pass arguments to the function. The call and apply methods invoke the function immediately, while the bind method returns a new function that can be invoked later.