Monkey Patching in JavaScript

Monkey patching in JavaScript is a programming technique that originates from the dynamic nature of the language.
The term “monkey patching” is borrowed from the world of software development, where it refers to the practice of modifying or extending code at runtime. In JavaScript, it allows developers to alter or extend the behavior of existing objects or classes without directly modifying their source code.

Monkey patching involves making changes to existing code, typically by adding new methods or properties to objects or classes, or by modifying existing ones. This can be done at runtime, allowing developers to augment functionality without altering the original code base. Monkey patching is often used to fix bugs, add missing features, or adapt third-party libraries to better suit specific requirements.

Example: We have an original calculator object with an add method. We then monkey patch the calculator object by adding a subtract method. So, we can now use both the add and subtract methods on the calculator object.

JavaScript

// Original object
const calculator = {
    add: function (a, b) {
        return a + b;
    }
};

// Monkey patching to add a new method
calculator.subtract = function (a, b) {
    return a - b;
};

console.log(calculator.add(5, 3));
console.log(calculator.subtract(5, 3));

Output

8
2

Pros of Monkey patching

• Monkey patching allows developers to extend or modify existing code without directly altering its source, providing flexibility in adapting libraries or frameworks to specific requirements.
• It enables quick fixes to issues or bugs in third-party code without waiting for official updates or patches.
• Developers can experiment with new features or enhancements without committing to permanent changes in the code base.

Cons of Monkey patching

• Overuse of monkey patching can lead to code base complexity and reduced readability, making it harder to understand and maintain.
• Modifying existing code at runtime can introduce unintended side effects or conflicts, especially in large or collaborative projects.
• Tracking down issues stemming from monkey-patched code can be challenging, particularly if the changes are distributed across multiple files or modules.

Conclusion

Monkey patching in JavaScript offers a powerful way to extend or modify existing code at runtime, providing flexibility and agility in software development. While it can be a valuable tool for quick fixes and experimental enhancements, developers should exercise caution to avoid introducing code complexity, unintended side effects, and debugging challenges. By using monkey patching judiciously and documenting changes effectively, developers can uses its benefits while minimizing potential drawbacks.