JavaScript Array

I reimplemented all 38 JavaScript Array functions (e.g. .forEach(), .map(), .sort(), etc.) with while loops only. As always, I learned something as I work on the all the functions. Some features, edge cases, considerations that I previously do not know about JavaScript.

If you are interested, read about my learning on my blog. I share what I learn about sparse arrays, copy of a reference, explained some algorithms, my thoughts on JavaScript language design, and many more.

Implementation Considerations

The major change I made is I wrote an object (MyArray) that contains functions as parameters (e.g. MyArray.at(array, 0)), rather than defining those functions as methods of an object (e.g. array.at(0)). Therefore, the first argument of all the functions is always the input array. I do not need to override the original methods. The built-in Array class is still used to construct the array, but none of the prototype functions are modified or used.

const array = ["a", "b", "c"];

// original function
const expected = array.join();

// my function
const actual = MyArray.join(array);

This makes it easier to test too. The actual value can be directly compared with the expected value.

• MyArray is implemented in array.ts
• All tests are written in array.test.ts
• index.ts is for testing manually

Read more in my blog!

Getting Started

To install dependencies:

bun install

To test:

bun test

I used bun to run and test the code. It is fast, simple to use, support TypeScript, and provide a test runner out of the box.

Notes

This is just a fun challenge I set for myself. I am not confident that it is absolutely correct, and I am sure you could find improvements in both time and memory complexity if you wanted to.