Static Members

Static functions and properties are declared in the class body but don't need created instances for their usage.

Static Properties

Static properties store value about the class. The value is specific for the class.

Static properties are declared via the keyword static.

The syntax for declaring static property:

static memberName;

The syntax for setting value to static member is:

ClassName.memberName = value;

Here's an example:

class Car { static carsCount; constructor(modelValue) { console.log("Object created."); this.model = modelValue; // Increment static member: Car.carsCount++; } } // Set value to static member: Car.carsCount = 0; console.log("Initial Cars Count: " + Car.carsCount); // create instances: var carobj1 = new Car("Toyota Corolla"); var carobj2 = new Car("Peugeot 508"); var carobj3 = new Car("Renault Clio"); console.log("Final Cars Count: " + Car.carsCount);

Output:

Initial Cars Count: 0 Object created. Object created. Object created. Final Cars Count: 3

Couple of things to notice:

• When an object is created via the parametrized constructor (lines 5 - 13), the static member value is incremented (due to line 12).
• At line 17 an initial value is set to the static member.
• When the static member is printed for the first time (line 19), it's value is zero.
• After objects were created via the parametrized constructor, it's value has reached 3 - the count of the created objects.

Static Functions

Static functions cannot use non-static class properties though declared in class.

They are defined via the keyword static.

Syntax for defining:

static funcName(args) { // code }

Syntax for calling:

ClassName.funcName(args);

Here's an example:

class Person { static printHi() { console.log("Hello!"); } } Person.printHi();

Output:

Hello!