How to Use Static Variables in JavaScript?

In JavaScript, there is no direct way to define a static variable (a variable that belongs to a class rather than an instance of a class). However, you can achieve similar behavior by defining a property on the constructor function.

Here’s an example:

function User(name) {
  if (typeof User.counter == 'undefined') {
    User.counter = 0;
  }
  this.name = name;
  User.counter++;
}

let user1 = new User("John");
let user2 = new User("Jane");

console.log(User.counter); // Output: 2

In the example above, we define a property counter on the User constructor function. When we create an instance of User, we increment the counter property. Since the property is attached to the constructor function, it remains the same across all instances, giving the appearance of a static variable.

Note that this approach only works for properties that don’t depend on instance data. For properties that depend on instance data, you’ll need to use a different approach, such as defining a static method on the constructor function.