What's the best way to replace eval?

Question

I deal with a JavaScript code to improve. The idea here is to invoke functions dynamically.

Here is the code to replace:

//this.actionCallback return the name of the function to invoke
eval(this.actionCallback + "('testArgument')");

What is the best way to replace it:

This way:

window[this.actionCallback]("testArgument");

Or this way:

var actionToCall = this.actionCallback+'("testArgument");';
var functionToInvoke = new Function(actionToCall);
functionToInvoke();

Or is there is a better way to do this?

Answer 1

The first way is a much better method - new Function(actionToCall) is just eval in disguise.

Answer 2

Both of the alternatives you have mentioned are not equivalent to the first one:

• Your first alternative requires that the function name be the member of window (in other words, defined at global scope). Having a function inside another scope will cause this to fail, but it doesn't use eval. :)

• Your second alternative creates a function object using the Function() constructor, so this also only works when the function in declared at the global scope, because a function defined by a Function constructor does not inherit any scope other than the global scope, and as said in Jamie Wong's answer, using the Function() constructor is still considered as eval :(

Here is an alternative that should work like your first one, but looks slightly better, but still uses eval.

eval(this.actionCallback)("testArgument");

But the best way is that this.actionCallback should be a real function object, and not just a function's name, then you can call:

this.actionCallback("testArgument");