Welcome to the Custom JavaScript Functions package! This npm package provides custom implementations of built-in JavaScript functions, allowing users to understand how these functions work internally. This is especially useful for learning purposes and for those who want to see how common JavaScript functions can be replicated.

Features 🚀

• Custom Implementations: Each function in this package is a custom implementation that mimics the behavior of the native JavaScript functions.
• Educational: The primary goal of this package is to provide an educational resource for developers to understand the inner workings of JavaScript functions.
• Polyfill-style Functions: These implementations can serve as polyfills, helping developers use similar functionality in environments where certain features may not be available.

Project Tree 🌳

📦 js-internals
│
├── 📂 src
│   ├── 📂 DataStructures
│   │   └── 📄 set.js
│   ├── 📂 internal-custom-functions
│   │   ├── 📂 Array_Object
│   │   │   ├── 📂 Instance_Methods
│   │   │   │   ├── 📄 _map.js
│   │   │   │   ├── 📄 _filter.js
│   │   │   │   └── 📄 _reduce.js
│   │   │   └── 📂 Static_Methods
│   │   │       ├── 📄 _call.js
│   │   │       ├── 📄 _apply.js
│   │   │       ├── 📄 _from.js
│   │   │       └── 📄 _isArray.js
│   └── 📄 index.js
│
├── 📂 tests
│   ├── 📄 test.js
│
├── 📄 package.json

Sample Code of custom $call(context, ...args) [Same as native call()]

/**
 * Function.prototype.call() - Calls a function with a given 'this' value and arguments provided individually.
 * The "call()" method allows you to invoke a function with a specific 'this' context, along with arguments passed individually. It is useful when you want to change the context ('this') for a particular function invocation.
 * @syntax :
 * @function.call(thisArg, arg1, arg2, ..., argN);

 * @thisArg : The value to use as 'this' when calling the function. If 'thisArg' is 'null' or 'undefined', it will default to the global object ('globalThis' in non-strict mode).
 * @arg1 , arg2, ..., argN: Individual arguments to pass to the function.

 * @returns:
 * The result of calling the function with the provided 'this' value and arguments.
**/

Function.prototype.__call = function(context, ...args) {
    if (typeof this !== "function") {
        throw new Error(this + " is not a function.");
    }

    if (context === undefined || context === null) {
        return this.apply(globalThis, args);
    }

    const boundContext = Object(context);

    boundContext.func = this;
    const result = boundContext.func(...args);
    delete boundContext.func;

    return result;
};

Progress ✨ ~

Available Functions 🚀

Array Methods

Function	Status	Native Function
$Map(array, callback)	Implemented	Array.prototype.map()
$Filter(array, callback)	Implemented	Array.prototype.filter()
$Reduce(array, callback, initialValue)	Implemented	Array.prototype.reduce()
$Array.from(value)	Implemented	Array.from()
$Array.isArray(array)	Implemented	Array.isArray()
$Array.of(value)	Implemented	Array.of()
$ForEach(array, callback)	Todo	Array.prototype.forEach()
$Some(array, callback)	Todo	Array.prototype.some()
$Every(array, callback)	Todo	Array.prototype.every()
$Find(array, callback)	Todo	Array.prototype.find()
$IndexOf(array, element)	Todo	Array.prototype.indexOf()
$Includes(array, element)	Todo	Array.prototype.includes()
$Sort(array, compareFunction)	Todo	Array.prototype.sort()
$Reverse(array)	Todo	Array.prototype.reverse()
$Splice(array, start, deleteCount, ...items)	Todo	Array.prototype.splice()
$Slice(array, start, end)	Todo	Array.prototype.slice()
$Concat(array, ...arrays)	Todo	Array.prototype.concat()
$Join(array, separator)	Todo	Array.prototype.join()

String Methods

Function	Status	Native Function
$CharAt(string, index)	Todo	String.prototype.charAt()
$IndexOf(string, searchValue, fromIndex)	Todo	String.prototype.indexOf()
$Includes(string, searchString, fromIndex)	Todo	String.prototype.includes()
$Slice(string, start, end)	Todo	String.prototype.slice()
$Substring(string, start, end)	Todo	String.prototype.substring()
$Trim(string)	Todo	String.prototype.trim()
$ToLowerCase(string)	Todo	String.prototype.toLowerCase()
$ToUpperCase(string)	Todo	String.prototype.toUpperCase()
$Split(string, separator, limit)	Todo	String.prototype.split()
$Replace(string, searchValue, newValue)	Todo	String.prototype.replace()

Object Methods

Function	Status	Native Function
$Keys(object)	Todo	Object.keys()
$Values(object)	Todo	Object.values()
$Entries(object)	Todo	Object.entries()
$Assign(target, ...sources)	Todo	Object.assign()
$Freeze(object)	Todo	Object.freeze()
$Seal(object)	Todo	Object.seal()
$GetOwnPropertyDescriptor(object, property)	Todo	Object.getOwnPropertyDescriptor()
$Create(prototype, properties)	Todo	Object.create()
$HasOwnProperty(object, property)	Todo	Object.prototype.hasOwnProperty()

Function Methods

Function	Status	Native Function
$Call(func, thisArg, ...args)	Implemented	Function.prototype.call()
$Apply(func, thisArg, args)	Implemented	Function.prototype.apply()
$Bind(func, thisArg, ...args)	Todo	Function.prototype.bind()

Math Methods

Function	Status	Native Function
$Max(...numbers)	Todo	Math.max()
$Min(...numbers)	Todo	Math.min()
$Floor(number)	Todo	Math.floor()
$Ceil(number)	Todo	Math.ceil()
$Round(number)	Todo	Math.round()
$Random()	Todo	Math.random()
$Abs(number)	Todo	Math.abs()

Other Global Functions

Function	Status	Native Function
$ParseInt(string, radix)	Todo	parseInt()
$ParseFloat(string)	Todo	parseFloat()
$IsNaN(value)	Todo	isNaN()
$IsFinite(value)	Todo	isFinite()
$Stringify(value)	Todo	JSON.stringify()
$Parse(jsonString)	Todo	JSON.parse()

Hello Devs 👋🏻 If you want to contribute you are always Welcome !! Come and Contribute Here > 3 💗🫠

Contribution Rule's

• maintain existing file naming convension (eg. _file.js)
• maintain existing code format for Contribution
• ensure you write all the import tests for that func maintaining the proper format (eg. test_funcName.js)
• demo test file for custom func $call()

const { __call } = require('../package/src/internal-custom-functions/Array_Object/Static_Methods/_call');

function deepEqual(obj1, obj2) {
    return JSON.stringify(obj1) === JSON.stringify(obj2);
}

// Run tests for the custom __call method
const tests = [
    {
        description: 'Basic Function Call with Context',
        func: function(greeting, punctuation) { return `${greeting}, ${this.name}${punctuation}`; },
        context: { name: 'Alice' },
        args: ['Hello', '!'],
        expected: 'Hello, Alice!',
        testNumber: 0
    },
    {
        description: 'Function with No Context',
        func: function(num1, num2) { return num1 + num2; },
        context: undefined,
        args: [5, 10],
        expected: 15,
        testNumber: 1
    }
    //Write atleast 7-8 proper test cases.
];

// Run the tests
tests.forEach(test => {
    let result;
    let errorOccurred = false;
    try {
        result = test.func.__call(test.context, ...test.args);
    } catch (error) {
        if (test.expectedError) {
            errorOccurred = true;
            console.log(`Passed Test${test.testNumber} ✅: ${test.description}`);
        } else {
            console.log(`Failed Test${test.testNumber} ❌: ${test.description}`);
            console.error('Unexpected Error:', error);
        }
    }

    if (!errorOccurred && deepEqual(result, test.expected)) {
        console.log(`Passed Test${test.testNumber} ✅: ${test.description}`);
    } else if (!errorOccurred) {
        console.log(`Failed Test${test.testNumber} ❌: ${test.description}`);
        console.log(`Expected: ${JSON.stringify(test.expected)}`);
        console.log(`Actual: ${JSON.stringify(result)}`);
    }
});

Project SetUp

First Clone The Repo

git clone https://github.com/Rudrajiii/Js-Internals

Then Move To Project Directory

cd Js-Internals

Now Open Your Favourite Code Editor [ Mine is Vs-Code :) So ]

code .

Installation ⏬

To install this package, use npm:

npm install --save-dev js-internals

To Run The Tests: Make the test script executable: For (Linux):

chmod +x pkg_tester.sh

Run the test script:

./pkg_tester.sh