Javascript closure: dynamically-defined functions, call method from current scope

Question

Is it possible to have a static function that calls a dynamically defined function? I need this because I can't change the static function, and all I know is that it calls the dynamic function. For example:

function staticFunc() {
  dynamicFunc();
}

function test() {
  function dynamicFunc() {console.log('yay');}
  staticFunc();
};

test();

but it gives me the error dynamicFunc is not defined.

I know that if I hardcode staticFunc in test(), it works. I also noticed that I only get the error when I call staticFunc, not when I define it (even though dynamicFunc is not defined yet), which makes it seem like staticFunc is running inside test()'s scope, but evidently not.

Any way to do this? The only way I can think of is to make a global function funcPtr that gets assigned to my dynamic function.

can you pass the "dynamicFunc" to teh "staticFunc" like staticFunc(dynamicFunc);? — fast
– fast, Commented Mar 20, 2014 at 11:43

Zaheer Ahmed · Accepted Answer · 2014-07-15 18:14:12Z

2

Closure is you can use variable of parent level scope in child level scope. Here in your case it is reverse you have initialize a function in a child level scope and try to invoke it in parent scope which is not correct.

You may pass current function as parameter and invoke it:

Here is Demo

function staticFunc(dynamicFunc) {
  dynamicFunc();
}

function test() {
  var dynamicFunc = function() {console.log('yay');}
  staticFunc(dynamicFunc);
};

test();

edited Jul 15, 2014 at 18:14

answered Mar 20, 2014 at 11:42

Zaheer Ahmed

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Comments

DontVoteMeDown · Accepted Answer · 2014-03-20 11:43:34Z

1

Try this:

var dynamicFunc = null;
function test() {
    dynamicFunc = function () {console.log('yay');}
    staticFunc();
};

Considering that you can't change anything on your static function, the solution changes the declaration of dynamicFunc to a var that contains a function.

This can throw an exception if the static function tries to call dynamicFunc when its null. But you can declare as this:

var dynamicFunc = function() {};

Fiddle.

answered Mar 20, 2014 at 11:43

DontVoteMeDown

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5 Comments

woojoo666 Over a year ago

thanks you, as I mentioned that was one of the solutions I was considering. I'd like to avoid polluting the global namespace as much as possible, but I guess you can't ask for too much :)

DontVoteMeDown Over a year ago

@woojoo666 I believe that is this case you have no choice =/

fast Over a year ago

@woojoo666 Overriding the "dynamicFunc" already referenced in the "static" does not pollute the global namespace, as the variable (dynFunc) is already defined globally; you will just overwrite that one.

woojoo666 Over a year ago

I was trying to avoid defining dynamicFunc globally in the first place

fast Over a year ago

wasn't the 'staticFunc' calling the 'dynamicFunc' given that way?? Generally, there should be no need to define such functs globally, question just is which is the scope, the two conceptually share..

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