11-12-2025

Bind, call, and apply

Javascript functions have access to three methods: call, bind, and apply.

These three methods control what this refers to inside a function.

call()

Invokes a function immediately with a specific this value.

function greet(greeting) {
  console.log(`${greeting}, I'm ${this.name}`);
}

const person = { name: 'Alice' };

greet.call(person, 'Hello');
// Output: "Hello, I'm Alice"

Arguments come individually, separated by commas.

apply()

Does the same thing as call(), but arguments come in an array.

function greet(greeting, punctuation) {
  console.log(`${greeting}, I'm ${this.name}${punctuation}`);
}

const person = { name: 'Bob' };

greet.apply(person, ['Hi', '!']);
// Output: "Hi, I'm Bob!"

bind()

Returns a new function with this permanently set.

It doesn't invoke the function immediately.

function greet(greeting) {
  console.log(`${greeting}, I'm ${this.name}`);
}

const person = { name: 'Charlie' };

const boundGreet = greet.bind(person);

boundGreet('Hey');
// Output: "Hey, I'm Charlie"

In Summary

• call: Run now, arguments one-by-one
• apply: Run now, arguments in an array
• bind: Create new function, run later