function-overloader

FUNCTION OVERLOADER

Introduce the mechanism for easy overloading functions and method.

install

npm install function-overloader

Introduction

This library/helper is solution for lack of function overloading in javascript. It will not introduce overloading for functions. But it will help handling multiple different arguments.

It will return response from correct do block.

teaser

import Overload from "function-overloader";
class Monster {

    constructor() {
        Overload
            .when(Overload.STRING, Overload.NUMBER)
            .do((monsterName, level) => {
                this.name = monsterName;
                this.level = level;
            })
            .when(Overload.OBJECT)
            .do(monsterData => {
                this.name = monsterData.name;
                this.level = monsterData.level;
            })
            .execute(...arguments);
        console.log(`Monster ${this.name} level ${this.level} created`);
    }
    
    addAttribute() {
        return Overload
            .when(Overload.INSTANCE(Attribute))
            .do(this.addExisitingAttribute)
            .when(Overload.STRING, Overload.FUNCTION)
            .do(this.addNewAttribute)
            .execute(...arguments);
    }
    
    addExisitingAttribute (attribute) {
        this.attributes.push(attribute);
        return attribute;
    }
    
    addNewAttribute (attributeName, attributeLogic) {
        const attribute = new Attribute(attributeName, attributeLogic);
        this.attributes.push(attribute);
        return attribute;
    }
}

Now it is possible:

    const monster1 = new Monster ("hakuna", 3);
    monster1.addAttribute("happy", () => {});
    const attribute = new Attribute("sad", () => {});
    monster1.addAttribute(attribute);
    
    const monster2 = new Monster ({
        name: "froggy",
        level: 2
    });

motivation

Decrease code complexity of overloaded functions and methods.

Old fashion:

function someMethod () {
    if(arguments.length === 2 && typeof arguments[0] === "string" && typeof arguments[1] === "number") {
        //do some stuff when get string and number
    } else if (arguments.length === 1 && typeof arguments[0] === "object" && arguments[0] instanceof SomeCustomConstructor) {
        //do something else if one argument which is instance of SomeCustomConstructor
    } else {
        //do something else
    }
}

usage

import/require this library

import Overload from "function-overloader";

then:

function someOverloadedFunction() {
    return Overload
        .when(<list of types>)
        .do(someFunctionHandlingFirstCase)
        .when(<list of types>)
        .do(someFunctionHandlingSecondCase)  
        .execute(...arguments);
}

API

.when()

.when()

It is for describe when to run related do method. Return object with do method

Accept multiple values that will descibe function. Possible values:

• Overload.ANY or Overload.ANY() for any type
• Overload.STRING or Overload.STRING() for string primitive and string object
• Overload.ARRAY or Overload.ARRAY() for arrays
• Overload.NUMBER or Overload.NUMBER() for number primitive and number object
• Overload.OBJECT or Overload.OBJECT() for objects with exception for null and primitive wrappers (primitive objects like Number, String, Boolean)
• Overload.FUNCTION or Overload.FUNCTION() for functions
• Overload.BOOLEAN or Overload.BOOLEAN() for boolean primitive and boolean object
• Overload.SYMBOL or Overload.SYMBOL() for symbols
• Overload.UNDEFINED or Overload.UNDEFINED() for undefined
• Overload.NULL or Overload.NULL() for null
• Overload.INTERFACE or Overload.INTERFACE(interfaceOptions) for checking if tested object has interface properties with correct types interfaceOptions is an object with property names and description example of interface

   interfaceOptions = {
       someProperty: Overload.NUMBER,
       otherProperty: Overload: STRING
   }
  

• Overload.INSTANCE(class) check if argument instance of class

if there is no arguments it means that it will resolve only when overloaded function doesn't get any arguments.

.else()

.else()

Accept callback function. Will invoke it when other criteria are not met.

Return object with done method.

.elseThrow()

.elseThrow()

Throws TypeError if not any above condition met

Return object with done method.

.execute()

.execute()

accept function arguments. It is possible by passing them one by one, but preferred why is to just pass spread ...arguments. Will return funtion response

.do()

Is accessible only from object returned from .when method

.do()

Accept callback function which should be called if previous .when match arguments. Will respond with Condition Response

License

MIT