new Function() does not work as expected

[espruino-discuss]

Posted at 2015-03-15 by net-tobi

Hello,

when I execute the following code in the browser or in Node.js, I see the console log with the value 4. In Espruino nothing happens. Do you have an idea why?

var x = new Function([ 'a' ], 'console.log(a);');
x.apply({}, [ 4 ]);

Best,

Tobias

[gfwilliams]

Posted at 2015-03-16 by @gfwilliams

Hi Tobias,

I've just checked, and it's an issue with Espruino's implementation of the Function constructor. Basically it only looks for the code to run, and not for the optional list of arguments.

So (new Function('console.log("Hello");'))() will work, but you won't be able to supply arguments.

I've filed a bug for it here: espruino/Espruino#505

If you want to work around it you could do:

function newFunction(args, code) {
  return eval("(function("+args.join(",")+"){"+code+"})");
}
var x = newFunction([ 'a' ], 'console.log(a);');
x.apply({}, [ 4 ]);