access-modifiers
v0.0.4
Published
easy use private/protected field for ES2015 class syntax
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access-modifiers 
日本語で読みたい方はこちら => README_JP
Introduction
easy use private/protected field for ES2015 class syntax
We should have complicated implementations to achieve private/protected access modifiers for ES2015 because of it has no such features for class syntax. This module reduces the complication of the implementation for access modifiers.
npm install access-modifiersYou can add --save or --save-dev option for your project needs.
:warning:Requirements
The module requires ES2015 Proxy.You should use a polyfill like tvcutsem/harmony-reflect if your expecting environment is not support the native Proxy.
The module also requires Symbol implementation.You can use a polyfill like medikoo/es6-symbol.In addition, the module is well suited to class syntax. To use the class syntax, you can use Babel.
Usage (Node.js)
Animal.js
import AccessModifiers from "access-modifiers";
// the `create` method returns the objects for private and protected modifiers
const [_,p] = AccessModifiers.create();
class Animal{
constructor(age){
this[_.age] = age; // access to a private field
this[p.name] = "Animal"; // access to a protected field
}
get age(){
return this[_.age];
}
get name(){
return this[p.name];
}
// restores the field information in a public method
introduce(){
return `Hello, my name is ${this.name}(age: ${this.age}).`;
}
}
// finally, registers the objects for private and protected modifiers used on the Animal class
AccessModifiers.register([_,p], Animal);
export default Animal;Gorilla.js
import AccessModifiers from "access-modifiers";
import Animal from "./Animal.js";
// you should give a base class to the `create` method for inheritance
const [_,p] = AccessModifiers.create(Animal);
class Gorilla extends Animal{
constructor(age){
super(age);
this[_.like] = "Banana"; // access to a private field
this[p.name] = "Gorilla"; // access to a protected field (overrides the Animal's field)
}
get like(){
return this[_.like];
}
// overrides a public method (rewrite the protected `name` field used in the `super.introduce` method)
introduce(){
return `${super.introduce()} I like a ${this.like}.`;
}
}
// finally, registers the objects for private and protected modifiers used on the Gorilla class
AccessModifiers.register([_,p], Gorilla);
export default Gorilla;index.js
import "harmony-reflect"; // you do not have to this line if the native Proxy is supported
import Animal from "./Animal.js";
import Gorilla from "./Gorilla.js";
const animal = new Animal(5);
console.log(animal.introduce()); // "Hello, my name is Animal(age: 5)."
animal.age = 10; // cannot set the value because the `age` is getter property
console.log(animal.age); // 5
const gorilla = new Gorilla(8);
console.log(gorilla.introduce()); // "Hello, my name is Gorilla(age: 8). I like a Banana."
// you can forcefully get the field values for Reflection
console.log(Object.getOwnPropertySymbols(gorilla)); // [symbol(name), symbol(age), symbol(like)]Usage (Browsers supporting Proxy)
<!DOCTYPE html>
<html lang="ja">
<head>
<!-- ensure to load browser.min.js -->
<script src="release/access-modifiers.browser.min.js"></script>
<script>
// do same way
const[_,p] = AccessModifier.create();
class Animal{
// implementation
}
AccessModifier.register([_,p]);
</script>
<!-- ... -->
</head>
<body>
</body>
</html>Usage (Browsers not supporting Proxy)
You had better not to put a dummy Proxy
<!DOCTYPE html>
<html lang="ja">
<head>
<script src="release/access-modifiers.browser.min.js"></script>
<script>
// define the name of private/protected members as Array to the 1st arg for the `create` method
const [_,p] = AccessModifier.create([["age"],["name"]]);
// do same way
class Animal{
// implementation
}
AccessModifier.register([_,p]);
</script>
<!-- ... -->
</head>
<body>
</body>
</html>