In JSDK's world, everything is Class!
- *Note: all code of this guide are written in TypeScript*
## Definition of Class
The recommended full class name format is:
- {library-name}.{package-name}.{short-class-name}
Like this: JS.util.Strings
Let's learn to define a new class: WHO.virus.Convid19
```javascript
module WHO {
export namespace virus {
export class Convid19 {
}
}
}
```
For refering it by its short class name in other classes without import again, you can add one line:
```javascript
import Convid19 = WHO.virus.Convid19;
```
## Type Class
We knew Convid19 is a RNA virus, now define a type class RNA for it:
```javascript
module WHO {
export namespace virus {
export type RNA = JsonObject>;
}
}
import RNA = WHO.virus.RNA;
```
## Abstract Class and Interface
Then define an abstract class RNAVirusand an interface Cloneable:
```javascript
module WHO {
export namespace virus {
export interface Cloneable {
clone(): T[];
}
export abstract class RNAVirus implements Cloneable{
public readonly rna: RNA;
constructor(rna: RNA) {
this.rna = rna
}
}
}
}
import Cloneable = WHO.virus.Cloneable;
import RNAVirus = WHO.virus.RNAVirus;
```
As parent class of Convid19:
```javascript
export class Convid19 extends RNAVirus {
public clone(): this[] {
let arr = [];
for (i = 0, max = Random.number(9999,true); i <= max; i++) {
arr[i] = new Convid19(this.rna);
}
return arr
}
}
```
## Multiple Inheritance
The syntax of JS does not support multiple inheritance, but we can use the prototype chain to realize multiple inheritance in a disguised form. In JS, we call it Mixin.
For example, Convid19 class had inherited from RNAVirus class,
and we also want it to inherit from another class InfectiousVirus for gaining its infect method, then we can realize by Mixin:
```javascript
export class InfectiousVirus {
public infect() {
...
}
... //other methods
}
Convid19.mixin(InfectiousVirus, ['infect']); //Only mix the infect method
let c19 = new Convid19(...);
Konsole.print((c19).infect());
```
* The Mixin feature needs importing jsugar module.
## Enumeration Class
Finally define an enumeration class for all known convid viruses:
```javascript
export enum ConvidViruses {
'229E' = '229E',
OC43 = 'OC43',
NL63 = 'NL63',
HKU1 = 'HKU1',
SARS = 'SARS',
MERS = 'MERS',
CONVID19 = 'CONVID19'
}
```
## Class File Management
JSDK recommends to keep up with Java on class file organizations(slightly differents with Java):
> 1. A class file is BEST to contains only one main class and many subsidiary classes/interfaces/types.
>
> 2. A class file SHOULD be named by the short class name of its main class. For example: The file Strings.ts is named by the short name of JS.util.Strings.
>
> 3. A class file SHOULD be stored by the package names of its main class. For example: The file path of Strings.ts is "/util/Strings.ts".