Fundamentals of Programming: Global and Local Variables - Wikibooks, open books for an open world (2024)

FAQs

Should you avoid global variables in JavaScript? ›

This is because once a global variable is declared, it can easily be modified by any successive function or block defined within the script, or multiple scripts, and any variable name can be misspelled by mistake, resulting in debugging issues especially for large codebases.

In this article, we talked about global variables. We should use them sparingly since they can introduce bugs and reduce our code's modularity.

Use global variables until you are comfortable with passing arguments (variables) to other functions. The latter allows for modular programming where you can add a feature without disturbing a working program... simply make a function call to the new feature and "pass arguments" to the new feature, as in post #6.

Passing local variables as parameters to functions and using return values is another simple and great way to avoid global variables in C. By limiting their scope and passing them explicitly, we reduce the reliance on global states that can be altered anywhere and anyhow.

Any component that depends upon a global variable cannot truly be closed to modifications – a change in one component that causes the variable to be used in an unexpected way will break other components using the variable.

Manipulating global variables within functions in JavaScript can have several drawbacks, including loss of encapsulation, potential naming conflicts, reduced code readability, and hindered code organization.

To delete a global variable from the global variable list, move the cursor to the line that contains the variable name and press the Delete function key.

You can access the global variables from anywhere in the program. However, you can only access the local variables from the function. Additionally, if you need to change a global variable from a function, you need to declare that the variable is global. You can do this using the "global" keyword.

Global variables are considered when you want to use them in every function including main. Also remember that if you initialize a variable globally, its initial value will be same in every function, however you can reinitialize it inside a function to use a different value for that variable in that function.

Why do global variables make a program difficult to debug? ›

When a bug is related to a global variable, it can be difficult to identify where the error is occurring because the variable can be modified in many different parts of the program. This can lead to increased time spent on debugging and potentially more bugs in the program.

Minimizing the use of global variables by using local variables interacts with stack usage control. For example, stack size can determine the number of local and global variables that the code generator can allocate in the generated code. For more information, see Customize Stack Space Allocation.

Use Local Variables Instead

The idea is that the global variable gState is replaced by the local variable sState in the script of your main application stack.

The global object in JavaScript is available to all parts of your code. Any variables or functions inside the global object are in the global scope, which means you can use them in the functions, nested callbacks, and modules in your code — wherever they are.

Global variables can be altered by any part of the code, making it difficult to remember or reason about every possible use. Testing in programs using global variables can be a huge pain as it is difficult to decouple them when testing.

There are many reasons to avoid touching the global scope: Naming conflicts: The global scope is shared across all scripts on a web page. If you introduce new global variables or modify existing ones, you risk causing naming conflicts with other scripts or libraries used on the same page.