a.concat(b)

[crguezl]

@coromoto @AdrianMoraRodriguez @PSantanaGlez13

What happens when we combine a proxy "default" array with a "plain" array?

let a = [3,2,1, else x => x*x ];
let b = ["hello", "world"];
let c = a.concat(b);
let d = b.concat(a);

[AdrianMoraRodriguez]

This gives an error in d but the c is builded perfectly:

[ 3, 2, 1, 'hello', 'world' ]

In the d case, it gives the following error:

Uncaught TypeError: Cannot convert a Symbol value to a number
    at Object.get (REPL9:6:14)
    at Array.concat (<anonymous>)