30-seconds-of-code: Array concatenation

[konglx90]

First, thanks for your share, I have a question about Array concatenation.

When i run it in chrome console:

const ArrayConcat = (arr, ...args) => [...arr,...args]; 
ArrayConcat([1], [1, 2, 3, [4]]) 

// The answer is => [1, [1, 2, 3, [4]]]; 
// This is different from the document. -_-

// see the print
const AC = (arr, ...args) => {
    console.log(arr, args);
};
AC([1], [1, 2, 3, [4]]);  // [1] [[1, 2, 3, [4]]]
AC([1], [1, 2, 3, [4]], [5, 6]); // [1] [[1, 2, 3, [4]], [5, 6]]

Is anything wrong with me?

[Chalarangelo]

There's nothing wrong with your browser. This is a very interesting bug, thanks for the heads up!

[fejes713]

Nothing wrong with you. The [..arr, ..args] is simply the other way of writing Array.concat() for 2 arrays. The function in this state cannot make an array out of multiple subarrays.

[robertmcodes]

Could https://lodash.com/docs/#flatten help in this situation?

[RinatValiullov]

Why we must pass the second parameter of function as a spread?
I want a flat array, but get multidimensional one.

const concArrays = (oneArray, ...anotherArray) => [...oneArray, ...anotherArray];
concArrays([1], [2, 3, 4]) // -> [1, Array(3)];

But if i will make the second parameter without spread all will be ok:

const concArrays = (oneArray, anotherArray) => [...oneArray, ...anotherArray];
concArrays([1], [2, 3, 4]); // -> [1,2,3,4]

[Chalarangelo]

As far as I am concerned, the concatenation is problematic for one main reason (apart from the obvious one that being it not working as expected): We have not really improved over the native Array.concat(), so what we are doing is exactly the same thing. lodash's concat accepts a first argument that can be something apart from an array, for example.

Now, this is a problem because we are showing off a snippet that does not work properly and does nothing that JS cannot natively achieve. Therefore I am closing all related issues and removing the snippet. Move this discussion in #100 where we decide which lodash functions are too much of a polyfill to be implemented and we can decide if we want to start rewriting this or drop it forever.

[lock[bot]]

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