Problem Solving - Array Flatten

In Javascript we know that we can nest arrays inside of other arrays. For example, the following is a valid array in JavaScript

[1, 2, [3, 4], [5, 6], 7]

but you can imagine a case when you'd like to flatten an array, decompose it into just an array of elements, so...

[1, 2, [3, 4], [5, 6], 7]

would become

[1, 2, 3, 4, 5, 6, 7]

Challenge 1

Create a JavaScript file called flatten.js and implement the function below that flattens an array. For now, don't worry about arrays that are more than one level deep.

var flatten = function(arr){
    //flatten the array here

    return arr;
}

var myArr = [1, 2, [3, 4], [5, 6], 7];

console.log(flatten(myArr));
//output: [1, 2, 3, 4, 5, 6, 7]

HINT: There might be something useful in here.

Challenge 2

As we know, arrays in JavaScript can be nested as deeply as we want. So the input could be...

[1, 2, [3, 4], [5, [6]], 7]

or even something like...

[1, [2, [3, [4, [5]]], 6, [7]]]

Therefore, our function needs to be able to handle an array of any depth. Create a new function called flatten2 that flattens deeply nested arrays. So, both of the examples should be flattened to [1, 2, 3, 4, 5, 6, 7].