Spread element magically turns functions into 'not functions'

Question

Suppose I have this simple JavaScript function:

function returnArray(){
    return [1, 2, 3];
}

Further suppose that I then say

<         


        

Answer 1

Here is the error I get using node@6.10.3

if (rest.length!=0) return [2*num, ...double(rest)];  
                                        ^

TypeError: double(...)[Symbol.iterator] is not a function
    at double (/home/henrique/labs/test.js:4:41)
    at double (/home/henrique/labs/test.js:4:41)
    at Object. (/home/henrique/labs/test.js:7:1)
    at Module._compile (module.js:570:32)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.runMain (module.js:604:10)
    at run (bootstrap_node.js:390:7)

Which probably means that the result of the evaluation of some of your function call is not an iterable.

The error is here:

if (array.length===1) return 2*array[0];

Change to:

if (array.length===1) return [2*array[0]];

and it will work.