The question is to use reduce() to operate on an array of arrays and return a homogeneous array with no sub-arrays.
Eg - [1,2,[3,[4,5]]] will return [1,2,3,4,5].

Here is code that works, considering the sub-array itself is not another array of arrays-

var a = [3,[4,[5,[6,7]]]];

var b = 8;

var c = [9,10];

var x = []



var arr = [1,2,a,b,c];

arr = [1,2,3,4,c];



console.log(arr.reduce(function oneArray(a,b)

    {

        return a.concat(b); 

    },x))

Notice that I change my arr array as the code does not work for the first arr array i.e [1,2,a,b,c].
For arr [1,2,3,4,c] the object returned is [1,2,3,4,9,10]

Here is my attempt to make it work for the first arr-

function oneArray(a,b)

    {

        if (typeof b == object)

            b = b.reduce(oneArray(x,y),[]);

        return a.concat(b); 

    }



    console.log(arr.reduce(oneArray(a,b),x));

This gives me the error

Uncaught TypeError: [object Array] is not a function(anonymous function) @ Flattening.html:27

It interprets my function oneArray as an array not a function

I understand the problem comes from the fact that reduce can (I think) work only with a function defined as a parameter.
Does anyone have a solution so that I get [1,2,3,4,5,6,78,9,10] as my result working around the limitations of reduce() unless I missed something?