TypedProxy

A module checks out type of methods parameters and properties of Class by using es6 Proxy.

Installation

npm i typedproxy

Example

const Typed = require('typedproxy');
//MyClass declaration
const TypedMyClass = new Typed(MyClass, { 'nonZeroType' : (value) => { 
        if (value === 0 ) throw new TypeError('nonZeroTypeError');
    }
});
const typedInstance = new TypedMyClass();
typedInstance.nonZeroMethod(1);//ok
typedInstance.nonZeroMethod(0);//throw TypeError

Usage

Suppose you have a es-6 class named TestClass, which contains constructor, some static methods and properties(probably with getter and setter), methods and etc. Probably he is looks like class which i have described below:

class TestClass {
    constructor(strName){
        this.soname = strName;
    }
    static staticMethod(strSomeStaticString) {
        return strSomeStaticString;
    }
    calcSomething(uIntSomeValue){
        return uIntSomeValue;
    }
    get name(){
        if(this._name){
            return this._name;
        } else {
            return 'Name not defined';
        }
    }
    set name(strName){
        this._name = strName;
        return true;
    }
};

If you want check out type of parameters, when invoke methods (or set property value) of this class or instance of this class you may follow next steps:

Include typedproxy module in your application :

const Typed = require('typedproxy');

Decide which types you will use in your application (e.g. str, uInt), and describes object that represents this one:

const types = {
    'str': (value) => {
        const typeOfValue = {}.toString.call(value).slice(8, -1);
        if (typeOfValue !== 'String') {
            throw new TypeError(`str parameter must be String instance, not ${typeOfValue}`);
        }
    },
    'uInt': (value) => {
        const typeOfValue = {}.toString.call(value).slice(8, -1);
        if (typeOfValue !== 'Number') {
            throw new TypeError(`uInt parameter must be Number instance, not ${typeOfValue}`);
        }
    }
};

Create new typed class based on your class and types object that you have described above. :

const TypedTestClass = new Typed(TestClass, types);

The TypedTestClass is typed version of TestClass now and you can invoke static methods (including setter of properties and constructor) of him. If parameters passed into methods are not valid, it will throw an TypeError (based on types object). If number of parameters passed into methods is not correct, it will throw an RangeError (by default):

TypedTestClass.staticMethod('string'); //ok

TypedTestClass.staticMethod(1); //throw TypeError

TypedTestClass.staticMethod('string', 'string'); //throw RangeError

Create new typed instances, which represents TestClass instance with typed feature:

const typedInstance = new TypedTestClass('string');
typedInstance.calcSomething(1); //ok

but

typedInstance.calcSomething('string'); //throw TypeError

typedInstance.calcSomething(1, 2); //throw RangeError

Types

All types that you are planning to use in your application are described by types object. This is simple object wich contains type names and their check out functions. The first characters of the parameters used in your class methods, must match with the names of types. For example :

if you want to use your equalOneType than typed object may be looks like :

typed = {
    'equalOneType' : (value) => {
        if(value !== 1) {
            throw new TypeError(`equalOneType param must be equal 1, not ${value}`); 
        }
    }
};

and method must be looks like :

someMethod(equalOneTypeParam){
    this.count+=equalOneTypeParam;
}