One Pager Cheat Sheet

• This tutorial explains how to use the flat() function in Javascript to flatten nested arrays to a specific depthLevel and provides an example of how to implement your own version of this method.
• We can recursively iterate through an array and flat it to the given depthLevel, while pushing any non-array element directly into the result array.

This is our final solution.

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function flat(array, depthLevel = 1) {

    let result = [];

    array.forEach((item) => {

        // if the item of the main array is an array itself, call the method recursively 

        // to check the elements inside

        if (Array.isArray(item) && depthLevel > 0) {

            result.push(...flat(item, depthLevel - 1));

        } else result.push(item); // else, push the object into the result

    });

    return result;

}

Alright, well done! Try another walk-through.

If you had any problems with this tutorial, check out the main forum thread here.