Question

What is the difference between Call, Apply and Bind in Javascript?

Answer 1

The difference between Call, Apply and Bind can be explained with below examples,

Call: The call() method invokes a function with a given this value and arguments provided one by one

var employee1 = { firstName: "John", lastName: "Rodson" };
var employee2 = { firstName: "Jimmy", lastName: "Baily" };

function invite(greeting1, greeting2) {
  console.log(
    greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
  );
}

invite.call(employee1, "Hello", "How are you?"); // Hello John Rodson, How are you?
invite.call(employee2, "Hello", "How are you?"); // Hello Jimmy Baily, How are you?

Apply: Invokes the function with a given this value and allows you to pass in arguments as an array

var employee1 = { firstName: "John", lastName: "Rodson" };
var employee2 = { firstName: "Jimmy", lastName: "Baily" };

function invite(greeting1, greeting2) {
  console.log(
    greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
  );
}

invite.apply(employee1, ["Hello", "How are you?"]); // Hello John Rodson, How are you?
invite.apply(employee2, ["Hello", "How are you?"]); // Hello Jimmy Baily, How are you?

bind: returns a new function, allowing you to pass any number of arguments

var employee1 = { firstName: "John", lastName: "Rodson" };
var employee2 = { firstName: "Jimmy", lastName: "Baily" };

function invite(greeting1, greeting2) {
  console.log(
    greeting1 + " " + this.firstName + " " + this.lastName + ", " + greeting2
  );
}

var inviteEmployee1 = invite.bind(employee1);
var inviteEmployee2 = invite.bind(employee2);
inviteEmployee1("Hello", "How are you?"); // Hello John Rodson, How are you?
inviteEmployee2("Hello", "How are you?"); // Hello Jimmy Baily, How are you?

Call and apply are pretty interchangeable. Both execute the current function immediately. You need to decide whether it’s easier to send in an array or a comma separated list of arguments. You can remember by treating Call is for comma (separated list) and Apply is for Array.

Whereas Bind creates a new function that will have this set to the first parameter passed to bind().