Question

If I have a variable containing a string, is there a way that I can treat the contents of that string as the name of a type?

For example, is there a ???? in Javascript such that:

var ts = "Array";
var magic_type = ????; //magic
var obj_instance = new magic_type;

is valid and obj_instance == [] ?

Answer 1

You can instantiate it by using bracket notation with the global object.

var arr = new window['Array'];

jsFiddle.

If the constructor takes arguments, add them to the end.

As a side note, your code example…

obj_instance === []

…won’t ever evaluate to true because the [] syntax will create a new Array with a different memory location.