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Javascript Set Global Variable: Javascript Explained

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It’s no secret that javascript is an important part of web development and programming, and the ability to set global variables is a vital part of the language. In this article, we’ll discuss what global variables are, how to set them in javascript, their benefits and pitfalls, examples of how they are used, strategies for managing global variables, and finally a summary of the process.

What is a Global Variable?

A global variable is a type of variable that is available to any part of a program, regardless of scope. This means that a global variable is declared outside the scope of any function or code block and can be referenced inside any function or code block. This makes global variables particularly useful for sharing data between multiple functions, or for providing persistent data between multiple sessions.

Global variables are often used to store values that are used throughout a program, such as a user’s name or a configuration setting. They can also be used to store data that is shared between multiple programs, such as a database connection or a shared memory segment. Global variables are also useful for passing data between functions, as they can be accessed from any part of the program.

How to Set Global Variables in Javascript

In javascript, global variables can be created by simply declaring them outside the scope of any functions or code blocks. All you need to do is define the variable and assign it a value. Here’s an example:

var myGlobalVariable = "Some Value";

Once declared, this variable can be accessed and modified inside any function or code block within the program. For example:

function myFunction(){  console.log(myGlobalVariable); }

The above example will log the value of our global variable to the console whenever the myFunction() function is called.

It is important to note that global variables are accessible from anywhere in the program, so it is important to use them responsibly. If you are not careful, you can end up with a lot of unexpected behavior in your code. It is best practice to use global variables only when absolutely necessary.

Benefits of Using Global Variables

The most obvious benefit of using global variables is that they allow for data to be shared between different functions in a program, which is a great way to reduce the complexity of the program. Global variables also provide the ability to persist data between multiple sessions, which is beneficial for applications that require user data, such as web applications.

Another advantage of using global variables is that they can be used to store configuration settings that can be accessed by multiple functions. This is especially useful for applications that require a lot of configuration settings, as it allows for a single source of truth for all of the settings. Additionally, global variables can be used to store data that is used across multiple functions, such as a database connection or a user’s session data.

Potential Pitfalls of Using Global Variables

While global variables are often necessary and useful in programming, it is important to understand some of their potential pitfalls. The main problem with global variables is that they can be accessed and modified anywhere in the program. This can lead to unintended side effects if the code is not written properly, as a change in a global variable may affect an unrelated part of the program. It is also important to be aware that global variables can be difficult to debug if there are unexpected side effects, as they can span multiple functions and multiple files. Finally, global variables can make the code more difficult to maintain and scale, as changes in the global variable may require changes in multiple functions.

In addition, global variables can be difficult to test, as they can be difficult to isolate and mock. This can lead to tests that are not reliable, as they may not accurately reflect the behavior of the code in a real-world environment. Furthermore, global variables can lead to code that is difficult to read and understand, as it can be difficult to keep track of which variables are global and which are local. For these reasons, it is important to be aware of the potential pitfalls of using global variables and to use them judiciously.

Examples of Global Variables in Javascript Code

Here are a few examples of how global variables are used in Javascript code:

  • Creating a global variable for a user cookie:
    var userCookie = "some value"
  • Creating a global variable that can be accessed by multiple functions:
    var myGlobalValue = "some value" function myFunction1(){  console.log(myGlobalValue); } function myFunction2(){  console.log(myGlobalValue); }
  • Creating a global variable that persists data between sessions:
    var myPersistentValue = "some value"

Global variables are also useful for storing data that needs to be accessed across multiple pages or functions. For example, if you need to store a user’s preferences or settings, you can create a global variable to store this information and access it from any page or function.

Strategies for Managing Global Variables

There are several strategies for managing global variables responsibly in javascript code. First, try to limit the number of global variables used in a program. This will reduce the likelihood of unintended side effects and make debugging easier. Second, always strive for clear and meaningful variable names. This helps make the code more readable and makes debugging easier. Third, if you do use multiple global variables, it may be helpful to create an object containing all the variables and using dot notation to access and modify them.

Finally, it is important to be aware of the scope of the variables you are using. Global variables are accessible from anywhere in the code, so it is important to be aware of how they are being used and how they may affect other parts of the program. By following these strategies, you can ensure that your code is well-structured and easy to maintain.

Summary of Javascript Set Global Variable

In summary, setting global variables in javascript is an important part of programming and web development. Global variables can be declared outside the scope of any function or code block, and they can be useful for sharing data between functions or for persisting data between multiple sessions. It is important to understand the potential pitfalls associated with global variables, such as their potential for unintended side effects, their difficulty to debug, and the fact that changes in global variables may require changing multiple functions. Finally, there are strategies for managing global variables responsibly such as limiting the number of global variables used in a program and always striving for clear and meaningful variable names.

It is also important to consider the scope of the global variable when declaring it. If the variable is intended to be used across multiple files, it should be declared in the global scope. If the variable is intended to be used within a single file, it should be declared in the local scope. Additionally, it is important to consider the security implications of global variables, as they can be accessed by any code in the application.

Nisha Kumari

Nisha Kumari

Nisha Kumari, a Founding Engineer at Bito, brings a comprehensive background in software engineering, specializing in Java/J2EE, PHP, HTML, CSS, JavaScript, and web development. Her career highlights include significant roles at Accenture, where she led end-to-end project deliveries and application maintenance, and at PubMatic, where she honed her skills in online advertising and optimization. Nisha's expertise spans across SAP HANA development, project management, and technical specification, making her a versatile and skilled contributor to the tech industry.

Written by developers for developers

This article was handcrafted with by the Bito team.

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