Why is extending native objects a bad practice?

by

When you extend an object, you change its behaviour.

Changing the behaviour of an object that will only be used by your own code is fine. But when you change the behaviour of something that is also used by other code there is a risk you will break that other code.

When it comes adding methods to the object and array classes in javascript, the risk of breaking something is very high, due to how javascript works. Long years of experience have taught me that this kind of stuff causes all kinds of terrible bugs in javascript.

If you need custom behaviour, it is far better to define your own class (perhaps a subclass) instead of changing a native one. That way you will not break anything at all.

The ability to change how a class works without subclassing it is an important feature of any good programming language, but it is one that must be used rarely and with caution.

More Related Contents:

  1. What are the nuances of scope prototypal / prototypical inheritance in AngularJS?
  2. __proto__ VS. prototype in JavaScript
  3. Properties of Javascript function objects
  4. Grasping prototypical Inheritance through pseudoclassical instantiation (JavaScript)
  5. How to access object prototype in javascript?
  6. prototypal inheritance concept in javascript as a prototype based language
  7. Prototypical inheritance – writing up [duplicate]
  8. Use of ‘prototype’ vs. ‘this’ in JavaScript?
  9. Crockford’s Prototypal inheritance – Issues with nested objects
  10. Javascript object members that are prototyped as arrays become shared by all class instances
  11. Defining methods via prototype vs using this in the constructor – really a performance difference?
  12. Assigning prototype methods *inside* the constructor function – why not?
  13. JS : Convert Array of Strings to Array of Objects
  14. ES6 arrow functions not working on the prototype?
  15. Extending an Object in Javascript
  16. Why use Object.prototype.hasOwnProperty.call(myObj, prop) instead of myObj.hasOwnProperty(prop)?
  17. Javascript when to use prototypes
  18. Setting methods through prototype object or in constructor, difference? [duplicate]
  19. Update parent scope variable in AngularJS
  20. Can I construct a JavaScript object without using the new keyword?
  21. Good Example of JavaScript’s Prototype-Based Inheritance
  22. ‘this’ keyword, not clear
  23. Adding Prototype to JavaScript Object Literal
  24. Performing inheritance in JavaScript
  25. Is John Resig’s Javascript inheritance snippet deprecated?
  26. this Vs. prototype [duplicate]
  27. Extending core types without modifying prototype
  28. Can you create functions with custom prototypes in JavaScript?
  29. Advantages of setting the “constructor” Property in the “prototype”
  30. What does the new keyword do under the hood?

Leave a Comment