How to Create Method in JavaScript Class: Simple Guide

In JavaScript, you create a method inside a class by defining a function directly within the class body using methodName() { } syntax. This method can then be called on instances of the class using instance.methodName().

Syntax

A method in a JavaScript class is defined by writing the method name followed by parentheses and curly braces inside the class body. It looks like a function but without the function keyword.

• class: keyword to declare a class.
• methodName(): the name of the method followed by parentheses.
• { }: curly braces contain the code the method runs.

javascript

class MyClass {
  methodName() {
    // code to run
  }
}

Example

This example shows a class Car with a method startEngine. When called, it prints a message to the console.

javascript

class Car {
  startEngine() {
    console.log('Engine started');
  }
}

const myCar = new Car();
myCar.startEngine();

Output

Engine started

Common Pitfalls

Common mistakes include:

• Using the function keyword inside a class method (not needed).
• Forgetting to create an instance before calling the method.
• Calling the method without parentheses, which returns the function itself instead of running it.

javascript

/* Wrong: Using function keyword inside class */
class WrongClass {
  sayHi() {
    console.log('Hi');
  }
}

/* Right: Method without function keyword */
class RightClass {
  sayHi() {
    console.log('Hi');
  }
}

const obj = new RightClass();
obj.sayHi(); // Correct way to call method

Output

Hi

Quick Reference

Remember these points when creating methods in JavaScript classes:

• Define methods without the function keyword.
• Call methods on instances, not on the class itself.
• Use parentheses () to invoke methods.

Key Takeaways

Define methods inside classes using methodName() { } syntax without the function keyword.

Create an instance of the class before calling its methods.

Always use parentheses to call a method, like instance.methodName().

Class methods are like functions tied to objects created from the class.

Avoid syntax errors by not using the function keyword inside class method definitions.