Instance methods in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an instance method in JavaScript?

An instance method is a function defined inside a class that can be called on objects created from that class. It operates on the data (properties) of the specific object.

beginner

How do you define an instance method inside a JavaScript class?

Inside a class, you write a function without the 'function' keyword. For example:<br><pre>class Dog {
  bark() {
    console.log('Woof!');
  }
}</pre>

beginner

Why do instance methods use 'this' keyword?

'this' refers to the specific object calling the method. It lets the method access or change that object's properties.

beginner

Can instance methods access properties of the object? How?

Yes, instance methods access properties using 'this.propertyName'. For example, if an object has a 'name' property, the method can use 'this.name' to get or set it.

beginner

What happens if you call an instance method without creating an object?

You get an error because instance methods belong to objects, not the class itself. You must create an object (instance) first to use them.

How do you call an instance method named 'greet' on an object 'person'?

A person.greet()

B greet.person()

C person->greet()

D greet()

You call instance methods using the object name followed by a dot and the method name with parentheses.

Where are instance methods defined in JavaScript?

A Outside the class

B Inside the object literal

C Inside the class body

D In the global scope

Instance methods are defined inside the class body so all objects created from the class can use them.

What does 'this' refer to inside an instance method?

A The global window object

B The class itself

C Undefined

D The object calling the method

'this' inside an instance method points to the specific object that called the method.

What happens if you try to call an instance method directly on the class without creating an object?

A Method runs normally

B Error or undefined behavior

C Creates a new object automatically

D Returns the method code as a string

Instance methods require an object to work on. Calling them on the class itself causes an error.

Which keyword is NOT used when defining an instance method inside a class?

A function

B methodName()

C this

D class

Inside a class, instance methods are defined without the 'function' keyword.

Explain what an instance method is and how it uses 'this' in JavaScript classes.

Think about how methods belong to objects created from classes.

Describe the steps to create a class with an instance method and call that method on an object.

Remember the order: class, method, object, call.