Break Hidden Dependencies for Cleaner Code TL;DR: Replace global variables with dependency injection to improve testability and reduce coupling. 💉 Problems Addressed 😔 Hidden Dependencies
Tight Coupling
Testing Challenges
Maintainability
Singletons Related Code Smells 💨 https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-vii-8dk31x0 https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiv https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxii Steps 🛠️ Identify global variables used across your codebase.
Create a real-world abstraction to encapsulate these variables.
Pass dependencies explicitly via function parameters or constructors.
Refactor existing code to use the new dependency-injected structure.
Remove the original global variable declarations. Sample Code 💻 Before ❌ // This global variable holds the API configuration  
const globalConfig = { apiUrl: "https://api.severance.com" };  

function fetchOuties() {  
  return fetch(`${globalConfig.apiUrl}/outies`);  
  // globalConfig is NOT passed as parameter
} After 👉 function fetchOuties(parameterConfig) {  
  return fetch(`${parameterConfig.apiUrl}/outies`);  
  // 1. Identify global variables
  // used across your codebase.
  // 4. Refactor the existing code 
  // to use the new dependency-injected structure. 
}  

const applicationConfig = { apiUrl: "https://api.severance.com" };  
// 2. Create a real-world abstraction
// to encapsulate these variables.

fetchOuties(applicationConfig); 
// 3. Pass dependencies explicitly 
// via function parameters or constructors.

//  const globalConfig = { apiUrl: "https://api.severance.com" };  
// 5. Remove the original 
// global variable declarations.

// Why Is 'config' a Dependency?
// Because:
// outies() depends on knowing the API URL to work
// Without this information, 
// The function can't perform its core task
// The dependency is 
// explicitly declared in the function signature A Step Beyond: API Reification class ApiService {
  constructor(parameterConfig) {
    this.variableConfig = parameterConfig;
  }
  
  // parameterConfig, variableConfig
  // and applicationConfig
  // are very bad names. 
  // They are here to emphasize the change

  fetchOuties() {
    return fetch(`${this.variableConfig.apiUrl}/outies`);
  }
}

const apiService = 
  new ApiService({ apiUrl: "https://api.severance.com" });
apiService.fetchOuties(); Type 📝 [x]Semi-Automatic Safety 🛡️ This refactoring is safe if you audit all global variable references and thoroughly test the code after injection. Why is the Code Better? 🌱 Testability: Dependencies can be replaced (not mocked) for unit tests. Explicit Contracts: Functions declare what they need. Scalability: Configuration changes don’t require code edits. Coupling: Code is less coupled. How Does it Improve the Bijection? 🗺️ By making dependencies explicit, the code mirrors real-world interactions where components rely on declared inputs, not hidden state. You also reduce Coupling which is usually the more important problem you must solve. Limitations ⚠️ Over-injection can lead to parameter bloat. Common Misconceptions "But it's just a parameter!" Exactly! Passing dependencies via parameters is Dependency Injection. Frameworks often obscure this basic principle. "This is too simple to be DI!" Dependency Injection doesn't require complex frameworks. This is a pure, framework-less injection. "Dependency Injection vs Dependency Inversion" Inversion is the principle (why). It tells you to depend on abstractions to reduce coupling.
Injection is the practice (how). It’s one way (there are many others) to apply the principle by passing dependencies from outside instead of creating them inside a class. Refactor with AI 🤖 You can use AI tools to analyze your codebase and identify global variables. The AI can suggest where to implement dependency injection and help generate the necessary interfaces or classes for your dependencies. Try Them! 🛠 Remember: AI Assistants make lots of mistakes Suggested Prompt: 1. Identify global variables used across your codebase.2. Create a real-world abstraction to encapsulate these variables. 3. Pass dependencies explicitly via function parameters or constructors. 4. Refactor existing code to use the new dependency-injected structure. 5. Remove the original global variable declarations. Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini



DeepSeek

DeepSeek



Meta AI

Meta AI



Qwen

Qwen Tags 🏷️ Dependency Injection Level 🔋 [x]Intermediate Related Refactorings 👩‍❤️‍💋‍� https://hackernoon.com/refactoring-018-how-to-replace-a-singleton?embedable=true https://refactoring.guru/es/introduce-parameter-object?embedable=true See also 🔍 https://hackernoon.com/coupling-the-one-and-only-software-designing-problem-9z5a321h?embedable=true https://hackernoon.com/singleton-pattern-the-root-of-all-evil-e4r3up7?embedable=true https://en.wikipedia.org/wiki/Dependency_injection?embedable=true https://en.wikipedia.org/wiki/Dependency_inversion_principle?embedable=true Credits 🙏 Image by Petra on Pixabay This article is part of the Refactoring Series. https://maximilianocontieri.com/how-to-improve-your-code-with-easy-refactorings?embedable=true Break Hidden Dependencies for Cleaner Code Break Hidden Dependencies for Cleaner Code TL;DR: Replace global variables with dependency injection to improve testability and reduce coupling. 💉 TL;DR: Replace global variables with dependency injection to improve testability and reduce coupling. 💉 Problems Addressed 😔 Hidden Dependencies Tight Coupling Testing Challenges Maintainability Singletons Hidden Dependencies Tight Coupling Coupling Testing Challenges Maintainability Singletons Singletons Related Code Smells 💨 https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-vii-8dk31x0 https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-vii-8dk31x0 https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiv https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiv https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxii Steps 🛠️ Identify global variables used across your codebase. Create a real-world abstraction to encapsulate these variables. Pass dependencies explicitly via function parameters or constructors. Refactor existing code to use the new dependency-injected structure. Remove the original global variable declarations. Identify global variables used across your codebase. Create a real-world abstraction to encapsulate these variables. Pass dependencies explicitly via function parameters or constructors. Refactor existing code to use the new dependency-injected structure. Remove the original global variable declarations. Sample Code 💻 Before ❌ // This global variable holds the API configuration  
const globalConfig = { apiUrl: "https://api.severance.com" };  

function fetchOuties() {  
  return fetch(`${globalConfig.apiUrl}/outies`);  
  // globalConfig is NOT passed as parameter
} // This global variable holds the API configuration  
const globalConfig = { apiUrl: "https://api.severance.com" };  

function fetchOuties() {  
  return fetch(`${globalConfig.apiUrl}/outies`);  
  // globalConfig is NOT passed as parameter
} After 👉 function fetchOuties(parameterConfig) {  
  return fetch(`${parameterConfig.apiUrl}/outies`);  
  // 1. Identify global variables
  // used across your codebase.
  // 4. Refactor the existing code 
  // to use the new dependency-injected structure. 
}  

const applicationConfig = { apiUrl: "https://api.severance.com" };  
// 2. Create a real-world abstraction
// to encapsulate these variables.

fetchOuties(applicationConfig); 
// 3. Pass dependencies explicitly 
// via function parameters or constructors.

//  const globalConfig = { apiUrl: "https://api.severance.com" };  
// 5. Remove the original 
// global variable declarations.

// Why Is 'config' a Dependency?
// Because:
// outies() depends on knowing the API URL to work
// Without this information, 
// The function can't perform its core task
// The dependency is 
// explicitly declared in the function signature function fetchOuties(parameterConfig) {  
  return fetch(`${parameterConfig.apiUrl}/outies`);  
  // 1. Identify global variables
  // used across your codebase.
  // 4. Refactor the existing code 
  // to use the new dependency-injected structure. 
}  

const applicationConfig = { apiUrl: "https://api.severance.com" };  
// 2. Create a real-world abstraction
// to encapsulate these variables.

fetchOuties(applicationConfig); 
// 3. Pass dependencies explicitly 
// via function parameters or constructors.

//  const globalConfig = { apiUrl: "https://api.severance.com" };  
// 5. Remove the original 
// global variable declarations.

// Why Is 'config' a Dependency?
// Because:
// outies() depends on knowing the API URL to work
// Without this information, 
// The function can't perform its core task
// The dependency is 
// explicitly declared in the function signature A Step Beyond: API Reification class ApiService {
  constructor(parameterConfig) {
    this.variableConfig = parameterConfig;
  }
  
  // parameterConfig, variableConfig
  // and applicationConfig
  // are very bad names. 
  // They are here to emphasize the change

  fetchOuties() {
    return fetch(`${this.variableConfig.apiUrl}/outies`);
  }
}

const apiService = 
  new ApiService({ apiUrl: "https://api.severance.com" });
apiService.fetchOuties(); class ApiService {
  constructor(parameterConfig) {
    this.variableConfig = parameterConfig;
  }
  
  // parameterConfig, variableConfig
  // and applicationConfig
  // are very bad names. 
  // They are here to emphasize the change

  fetchOuties() {
    return fetch(`${this.variableConfig.apiUrl}/outies`);
  }
}

const apiService = 
  new ApiService({ apiUrl: "https://api.severance.com" });
apiService.fetchOuties(); Type 📝 [x]Semi-Automatic [x] Semi-Automatic [x] Safety 🛡️ This refactoring is safe if you audit all global variable references and thoroughly test the code after injection. Why is the Code Better? 🌱 Testability: Dependencies can be replaced (not mocked ) for unit tests. mocked Explicit Contracts: Functions declare what they need. Scalability: Configuration changes don’t require code edits. Coupling: Code is less coupled. How Does it Improve the Bijection? 🗺️ By making dependencies explicit, the code mirrors real-world interactions where components rely on declared inputs, not hidden state. real-world You also reduce Coupling which is usually the more important problem you must solve. Coupling Limitations ⚠️ Over-injection can lead to parameter bloat . parameter bloat Common Misconceptions "But it's just a parameter!" Exactly! Passing dependencies via parameters is Dependency Injection. Frameworks often obscure this basic principle. Exactly! Passing dependencies via parameters is Dependency Injection . Frameworks often obscure this basic principle. Dependency Injection "This is too simple to be DI!" Dependency Injection doesn't require complex frameworks. This is a pure, framework-less injection. Dependency Injection doesn't require complex frameworks. This is a pure, framework-less injection. "Dependency Injection vs Dependency Inversion" Inversion is the principle (why). It tells you to depend on abstractions to reduce coupling. Injection is the practice (how). It’s one way (there are many others) to apply the principle by passing dependencies from outside instead of creating them inside a class. Inversion is the principle (why). It tells you to depend on abstractions to reduce coupling. Inversion Injection is the practice (how). It’s one way (there are many others) to apply the principle by passing dependencies from outside instead of creating them inside a class. Refactor with AI 🤖 You can use AI tools to analyze your codebase and identify global variables. The AI can suggest where to implement dependency injection and help generate the necessary interfaces or classes for your dependencies. Try Them! 🛠 Remember: AI Assistants make lots of mistakes Remember: AI Assistants make lots of mistakes Suggested Prompt: 1. Identify global variables used across your codebase.2. Create a real-world abstraction to encapsulate these variables. 3. Pass dependencies explicitly via function parameters or constructors. 4. Refactor existing code to use the new dependency-injected structure. 5. Remove the original global variable declarations. Suggested Prompt: 1. Identify global variables used across your codebase.2. Create a real-world abstraction to encapsulate these variables. 3. Pass dependencies explicitly via function parameters or constructors. 4. Refactor existing code to use the new dependency-injected structure. 5. Remove the original global variable declarations. Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini



DeepSeek

DeepSeek



Meta AI

Meta AI



Qwen

Qwen Without Proper Instructions

With Specific Instructions ChatGPT

ChatGPT Claude

Claude Perplexity

Perplexity Copilot

Copilot Gemini

Gemini DeepSeek

DeepSeek Meta AI

Meta AI Qwen

Qwen Without Proper Instructions With Specific Instructions Without Proper Instructions Without Proper Instructions With Specific Instructions With Specific Instructions ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT Claude Claude Claude Claude Claude Claude Claude Claude Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Copilot Copilot Copilot Copilot Copilot Copilot Copilot Copilot Gemini Gemini Gemini Gemini Gemini Gemini Gemini Gemini DeepSeek DeepSeek DeepSeek DeepSeek DeepSeek DeepSeek DeepSeek DeepSeek Meta AI Meta AI Meta AI Meta AI Meta AI Meta AI Meta AI Meta AI Qwen Qwen Qwen Qwen Qwen Qwen Qwen Qwen Tags 🏷️ Dependency Injection Dependency Injection Level 🔋 [x]Intermediate [x] Intermediate [x] Related Refactorings 👩‍❤️‍💋‍� https://hackernoon.com/refactoring-018-how-to-replace-a-singleton?embedable=true https://hackernoon.com/refactoring-018-how-to-replace-a-singleton?embedable=true https://refactoring.guru/es/introduce-parameter-object?embedable=true https://refactoring.guru/es/introduce-parameter-object?embedable=true See also 🔍 https://hackernoon.com/coupling-the-one-and-only-software-designing-problem-9z5a321h?embedable=true https://hackernoon.com/coupling-the-one-and-only-software-designing-problem-9z5a321h?embedable=true https://hackernoon.com/singleton-pattern-the-root-of-all-evil-e4r3up7?embedable=true https://hackernoon.com/singleton-pattern-the-root-of-all-evil-e4r3up7?embedable=true https://en.wikipedia.org/wiki/Dependency_injection?embedable=true https://en.wikipedia.org/wiki/Dependency_injection?embedable=true https://en.wikipedia.org/wiki/Dependency_inversion_principle?embedable=true https://en.wikipedia.org/wiki/Dependency_inversion_principle?embedable=true Credits 🙏 Image by Petra on Pixabay Petra Pixabay This article is part of the Refactoring Series. https://maximilianocontieri.com/how-to-improve-your-code-with-easy-refactorings?embedable=true https://maximilianocontieri.com/how-to-improve-your-code-with-easy-refactorings?embedable=true

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Refactoring 024 - Replace Global Variables with Dependency Injection

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