How to modify global variables and precautions

How to modify global variables. I need to understand their needs first. Maybe they encountered a situation during development where they needed to share data across modules, or wanted to configure some globally accessible settings. However, there may be some problems with global variables, such as naming conflicts, difficulty in maintaining and testing, so I have to remind them of these potential problems.

First, I should explain how global variables are defined in. For example, using global objects to add properties is like using window in a browser. For example = ‘value’;. However, it should be emphasized here that although this can be done, it should be used with caution and better alternatives such as module export, environment variables, or configuration management tools.

Then the user may need specific examples, I should give a code example of how to set and access global variables, and also illustrate the potential risks. For example, modifying the same global variable by multiple modules may lead to unforeseen side effects, especially in asynchronous operations, where state management can become complicated.

Next, I should discuss alternatives. For example, use modules to export singleton objects, so that state can be shared in different files while maintaining better encapsulation. Or use environment variables to pass configuration information, which is safer and easier to switch between different environments. In addition, libraries like dotenv can easily manage environment variables and avoid hard-code sensitive information in code.

The user may not realize the problem of global variables in cluster mode or child processes. For example, in the cluster module, each worker process has independent memory space and global variables will not be shared. At this time, inter-process communication or external storage, such as database or cache services, is required.

In addition, testing issues are also very important. Global variables may cause test cases to affect each other, destroying the isolation of tests. At this time, it is recommended to use dependency injection or pass configuration objects as parameters to improve the testability of the code.

Security, if sensitive information is stored in global variables, there may be a risk of leakage. Users should be reminded to avoid doing so and instead use encrypted environment variables or secure configuration management services.

Finally, to summarize, although modifications to global variables are allowed, they should be avoided as much as possible in practical applications and instead adopt a more modular and more maintainable approach. If necessary, ensure good documentation and strict naming specifications to reduce the possibility of conflict.

Modifying global variables in requires careful operation, but it can be done in the following ways. The following are detailed guidelines and precautions:

1. How to define global variables

The global object isglobal, similar to the browserwindowObject.

// Define global variables = {
  env: 'development',
  apiBaseUrl: ''
};
// Access in any file(); // Output: development

2. Modify the correct posture of global variables

1. Modify properties directly

// Modify existing global variable attributes = 'production';
// Add new attributes = 5000;

2. Replace the entire object

// Completely replace global variables = {
  env: 'staging',
  apiBaseUrl: ''
};

3. Hidden dangers and solutions of global variables

1. Naming conflict risk

Problem scenario: Multiple modules define global variables with the same name
Solution: Use a unique named prefix

global.__MYAPP_config = { ... }; // Use double underscore prefix

2. State pollution in asynchronous operation

Problem scenario：

// Error example: Multiple requests may overwrite global status = getUserFromRequest(req);
// Correct solution: Use closure or request context = getUserFromRequest(req);

3. The module hot update fails

Problem scenario: Modifying global variables will not trigger module reloading
Solution: Use the configuration management module

// (Support hot updates)let config = { ... };
 = {
  get: () => config,
  update: (newConfig) => { config = {...config, ...newConfig} }
};

4. Recommend alternatives

1. Environment variables (best practices)

// Access by.NODE_ENV = 'test'; 
// Use dotenv management (need to install npm package)require('dotenv').config();
(.DB_HOST);

2. Module export single case

// 
let config = { ... };
 = config;
// Modify in other filesconst config = require('./config');
 = true;

3. Use container objects

// Create global containers (safer than using global directly) = {
  cache: new Map(),
  dbConnPool: null
};
// Initialization operation = createPool();

5. Debugging skills

1. View all global variables

(global);

2. Detect global variable modifications

// Use Proxy to monitor changes = new Proxy({ value: null }, {
  set(target, prop, value) {
    (`Global variables are modified: ${prop}=${value}`);
    target[prop] = value;
    return true;
  }
});

6. Special precautions

1. Limitations in Cluster mode

const cluster = require('cluster');
if () {
   = createCache(); // The main process is valid} else {
  // The child process cannot access the main process's global variables  // Need to use IPC communication or shared storage (such as Redis)}

2. TypeScript support

// Global extension declaration (in . file)declare global {
  namespace NodeJS {
    interface Global {
      myCustomGlobal: string;
    }
  }
}
// use = "Hello TS";

Summary suggestions

Best Practice Principles：

• Prefer module scope rather than global scope
• Data that needs to be shared across modules is explicitly passed
• A unique named prefix must be added when using global variables
• Production environment avoids storing sensitive information through global

This is the end of this article about how to modify global variables. For more relevant content on modifying global variables, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!