JavaScript - Declaring Global Scope for Nested Function?

Question

My attempts at giving global scope to a nested JavaScript function are not working:

//DECLARE FUNCTION B IN GLOBAL SCOPE
function B;

function A() {

    //DEFIN         


        

Answer 1

function B; will simply generate a syntax error.

You can use a function expression. As functions are first class objects, you can assign a function to a variable:

var B; // declare (global) variable (outer scope)

function A() {
    // assign a function to it
    B = function() {
        alert("function B is running");
    };
}

// we have to call A otherwise it won't work anyway
A();
// call B
B();

You could also let A return a function:

function A() {
    return function() {
        alert("function B is running");
    };
}

B = A();

This would make the relation between A and B a bit clearer.

Of course you can always define a global variable by omitting var, but you should use this very carefully. Use as less global variables as possible.

function A() {
    B = function() {
        alert("function B is running");
    };
}

And I bet there is a better way of doing it, depending on what your actual goal is.

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