coding-challenges | bringing together some of the problems | Learning library

The main issue here is that your code seems to expect the network request to be synchronous (ie, that fulldata is populated after the xhttp.send() function call has been issued).

In order for your code to work as required, you should instead build the table "inside" of the onreadystatechange function handler (ie at the point when fulldata is populated). One approach to this would be as follows:

arr = arr.join(arr2) is not doing what you think it does--the .join method joins the elements in an array into a string delimited by the parameter. When you pass this string arr into the recursive function call, you'll get a crash on the next stack frame, because strings don't have a map function.

You probably meant .concat, which puts the elements from the parameter array on the back of the instance array. Here's a snippet to illustrate what's going on.