static members
Learn class-level methods and properties with static.
What is static?
When you write static before a member, it belongs to the class itself, not instances. You access it through the class name, not through an instance.
class MathHelper {
static PI = 3.14;
static square(n) {
return n * n;
}
}You call these members as MathHelper.PI or MathHelper.square(4).
Static vs instance members
Static members are called on the class name; instance members are called on an instance. They serve different purposes.
MathHelper.square(4); // static call
const m = new MathHelper();
m.square(4); // wrong: not via instanceHelper operations (math, conversion) are usually static; methods that need instance data stay as instance methods.
Exercise MathHelper class
Declare a MathHelper class. Add a static PI property set to 3.14. Add a static square(n) method that returns n * n.
Show example solution
First write static PI = 3.14, then static square(n) { return n * n; }.
Example solution:
class MathHelper {
static PI = 3.14;
static square(n) {
return n * n;
}
}Test yourself
-
How do you access a static method?
MathHelper.square(4)- through an instance
- through the class name
- through this
- by method name
Show answer
through the class name — Correct! Static methods are called on the class name.
-
Call the static method
const area = ____;Show answer
const area = MathHelper.square(4); -
Match the concepts
- static
- declares a class-level member
- ClassName.method()
- static method call
- this.method()
- instance method call
- static PI
- class-level constant