Toolbox Aid

October 20th, 2024 9:49 PM Mr. Q Categories: JavaScript

Topic: Global Variables

Global variables in JavaScript can be defined and accessed from any part of your code, making them useful but also potentially problematic. This post will cover how to define and use global variables, the impacts they can have on code organization, and best practices for minimizing their usage.

Command Description

1. Defining Global Variables: A global variable is declared outside of any function. It can be accessed anywhere in your code. In JavaScript, if a variable is declared using var or without a declaration keyword in the global scope, it becomes a global variable.
2. Impacts on Code Organization: While global variables can simplify access to shared data, they can also lead to code that is difficult to maintain, as changes to a global variable can have unintended side effects across the entire application.
3. Best Practices: It is generally advisable to minimize the use of global variables to reduce the risk of naming conflicts and improve code modularity. Use closures, modules, or function parameters to encapsulate data.

Sample Code

// Defining a global variable
var globalScore = 0; // Global variable

function updateScore(points) {
    globalScore += points; // Modifying the global variable
    console.log(`Score updated: ${globalScore}`);
}

function resetScore() {
    globalScore = 0; // Resetting the global variable
    console.log("Score reset");
}

updateScore(10); // Output: Score updated: 10
updateScore(5);  // Output: Score updated: 15
resetScore();    // Output: Score reset
updateScore(20); // Output: Score updated: 20

// Best Practices Example: Avoiding global variables
function createGame() {
    let localScore = 0; // Local variable within the function

    return {
        updateScore: function(points) {
            localScore += points; // Modify local variable
            console.log(`Local score updated: ${localScore}`);
        },
        resetScore: function() {
            localScore = 0; // Reset local variable
            console.log("Local score reset");
        }
    };
}

const game = createGame();
game.updateScore(10); // Output: Local score updated: 10
game.updateScore(5);  // Output: Local score updated: 15
game.resetScore();    // Output: Local score reset
game.updateScore(20); // Output: Local score updated: 20

Copy
001// Defining a global variable
002var globalScore = 0; // Global variable
003
004function updateScore(points) {
005    globalScore += points; // Modifying the global variable
006    console.log(`Score updated: ${globalScore}`);
007}
008
009function resetScore() {
010    globalScore = 0; // Resetting the global variable
011    console.log("Score reset");
012}
013
014updateScore(10); // Output: Score updated: 10
015updateScore(5);  // Output: Score updated: 15
016resetScore();    // Output: Score reset
017updateScore(20); // Output: Score updated: 20
018
019// Best Practices Example: Avoiding global variables
020function createGame() {
021    let localScore = 0; // Local variable within the function
022
023    return {
024        updateScore: function(points) {
025            localScore += points; // Modify local variable
026            console.log(`Local score updated: ${localScore}`);
027        },
028        resetScore: function() {
029            localScore = 0; // Reset local variable
030            console.log("Local score reset");
031        }
032    };
033}
034
035const game = createGame();
036game.updateScore(10); // Output: Local score updated: 10
037game.updateScore(5);  // Output: Local score updated: 15
038game.resetScore();    // Output: Local score reset
039game.updateScore(20); // Output: Local score updated: 20

Output

Score updated: 10
Score updated: 15
Score reset
Score updated: 20
Local score updated: 10
Local score updated: 15
Local score reset
Local score updated: 20

Copy
001Score updated: 10
002Score updated: 15
003Score reset
004Score updated: 20
005Local score updated: 10
006Local score updated: 15
007Local score reset
008Local score updated: 20

Use Case

• Game Development: Global variables may be tempting for storing shared game state, such as scores or player lives, but they can lead to unpredictable behavior as your game grows in complexity. For example, if multiple functions modify a global score variable, tracking down bugs can become challenging. Instead, using closures or encapsulating game state within objects can help manage state more effectively. This approach keeps your code organized and reduces the risk of unintended side effects, ultimately leading to a more maintainable codebase.