Inject variable into function's scope

Question

So, I want to do something like this:

    var a = 'a';

    var dummy = function() {

        // Print out var 'a', from the scope above
        console.log('Dummy a: ' + a);

        // Print out 'b', from the 'compelled' scope
        console.log('Dummy b: ' + b);
    }

    (function() {

        var b = 'otherscope';

        // I know apply won't work, I also don't want to merge scopes
        dummy.apply(this);

        // I want something like this:
        dummy.compel(this, [], {b: 'injected!'});

    })();

But that won't work.

I don't actually want a function to be able to reach 2 scopes, I DO want to be able to set the 'b' variable used inside the dummy function from the outside.

Answer 1

You can make b a parameter for the function, or a global variable.

var a = 'a';
var dummy = function(b) {
   ...
}

or

var a = 'a';
var b;
var dummy = function() {
   ...
}

The first allows you to choose when the dummy function has access to the variable, the second allows it to be accessed everywhere.