Is there a way to verify the existence of a global function in JavaScript?

There is a global function that I have defined:

GlobalFunctions = {
      something: function() {

      }
};

I am aware of how to check if a function exists using:

if (typeof functionName == "function")

or the preferred method:

if (typeof functionName === "function")

However, even though the above methods work fine, when attempting to validate a global function, I encounter this error:

if (typeof GlobalFunctions.something == "function")

This results in the following error:

angular.js:12520 ReferenceError: GlobalFunctions is not defined
    at r.$scope.continueLogout (my-app.js:197)
    at b.$scope.logout (my-app.js:243)
    at fn (eval at compile (angular.js:13365), <anonymous>:4:209)
    at e (angular.js:23613)
    at b.$eval (angular.js:16052)
    at b.$apply (angular.js:16152)
    at HTMLAnchorElement.<anonymous> (angular.js:23618)
    at HTMLAnchorElement.dispatch (jquery.min.js:3)
    at HTMLAnchorElement.q.handle (jquery.min.js:3)

I tried searching on Google for solutions related to global functions, but found only solutions for regular functions.

Hope that explanation was clear, thank you.

javascript

Answer №1

When declaring the object, it appears that you are not utilizing the var, let, or const keywords.
It seems likely that your code is running with 'use strict'.

In the absence of strict mode, you have the ability to declare variables without using the var keyword, resulting in the variable being set on the global object:

Firstly, strict mode prevents accidental creation of global variables. In regular JavaScript, a typo in a variable assignment can create a new property on the global object and still function as intended.

With strict mode: 

'use strict'
GlobalFunctions = {
      something: function() {

      }
};

if(GlobalFunctions) console.log('yeah');

Without strict mode: 

GlobalFunctions = {
      something: function() {

      }
};

if(GlobalFunctions) console.log('yeah');

Answer №2

Solution uncovered:

if (GlobalFunctions !== undefined)

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