Question

I have the name of a function in JavaScript as a string. How do I convert that into a function pointer so I can call it later?

Depending on the circumstances, I may need to pass various arguments into the method too.

Some of the functions may take the form of namespace.namespace.function(args[...]).

Answer 1

Don’t use eval unless you absolutely, positively have no other choice.

As has been mentioned, using something like this would be the best way to do it:

window['functionName'](arguments); 

That, however, will not work with a namespace’d function:

window['My.Namespace.functionName'](arguments); // fail 

This is how you would do that:

window['My']['Namespace']['functionName'](arguments); // succeeds 

In order to make that easier and provide some flexibility, here is a convenience function:

function executeFunctionByName(functionName, context /*, args */) {   var args = Array.prototype.slice.call(arguments, 2);   var namespaces = functionName.split('.');   var func = namespaces.pop();   for(var i = 0; i < namespaces.length; i++) {     context = context[namespaces[i]];   }   return context[func].apply(context, args); } 

You would call it like so:

executeFunctionByName('My.Namespace.functionName', window, arguments); 

Note, you can pass in whatever context you want, so this would do the same as above:

executeFunctionByName('Namespace.functionName', My, arguments);