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 instance

Helper 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

Next lesson: Summary - Classes

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