Accessing variables from other functions without using global variables

Question

I think your best bet here may be to define a single global-scoped variable, and dumping your variables there:

var MyApp = {}; // Globally scoped object

function foo(){
    MyApp.color = 'green';
}

function bar(){
    alert(MyApp.color); // Alerts 'green'
} 

No one should yell at you for doing something like the above.

To make a variable calculated in function A visible in function B, you have three choices:

• make it a global,
• make it an object property, or
• pass it as a parameter when calling B from A.

If your program is fairly small then globals are not so bad. Otherwise I would consider using the third method:

function A()
{
    var rand_num = calculate_random_number();
    B(rand_num);
}

function B(r)
{
    use_rand_num(r);
}

Consider using namespaces:

(function() {
    var local_var = 'foo';
    global_var = 'bar'; // this.global_var and window.global_var also work

    function local_function() {}
    global_function = function() {};
})();

Both local_function and global_function have access to all local and global variables.

Edit: Another common pattern:

var ns = (function() {
    // local stuff
    function foo() {}
    function bar() {}
    function baz() {} // this one stays invisible

    // stuff visible in namespace object
    return {
        foo : foo,
        bar : bar
    };
})();

The returned properties can now be accessed via the namespace object, e.g. ns.foo, while still retaining access to local definitions.

What you're looking for is technically known as currying.

function getMyCallback(randomValue)
{
    return function(otherParam)
    {
        return randomValue * otherParam //or whatever it is you are doing.
    }

}

var myCallback = getMyCallBack(getRand())

alert(myCallBack(1));
alert(myCallBack(2));

The above isn't exactly a curried function but it achieves the result of maintaining an existing value without adding variables to the global namespace or requiring some other object repository for it.

I found this to be extremely helpful in relation to the original question:

Return the value you wish to use in functionOne, then call functionOne within functionTwo, then place the result into a fresh var and reference this new var within functionTwo. This should enable you to use the var declared in functionOne, within functionTwo.

function functionOne() {
  var variableThree = 3;
  return variableThree;
}

function functionTwo() {
  var variableOne = 1;
  var var3 = functionOne();

  var result = var3 - variableOne;

  console.log(variableOne);
  console.log(var3);
  console.log('functional result: ' + result);
}

functionTwo();

If another function needs to use a variable you pass it to the function as an argument.

Also global variables are not inherently nasty and evil. As long as they are used properly there is no problem with them.