Why doesn’t equality check work with arrays [duplicate]

by

Javascript arrays are objects and you can’t simply use the equality operator == to understand if the content of those objects is the same. The equality operator will only test if two object are actually exactly the same instance (e.g. myObjVariable==myObjVariable, works for null and undefined too).

If you need to check if two array are equals i’d recommend to just traverse both arrays and verify that all the elements have the same value (and that the two array have the same length).

Regarding custom objects equality i’d build instead a specific equals function and i’d add it to the prototype of your class.

Considering that in the end you converted both arrays to a String and tested equality of the resulting strings, you could one day consider using a similar but more generic technique you’ll find described in more than a few places:

JSON.stringify(OBJ1) === JSON.stringify(OBJ2)

Well, don’t.

While this could work if the order of the properties will always the same for those object instances, this leaves the door open for extremely nasty bugs that could be hard to track down. Always favor a more explicit approach and just write a clean and readable function that will test for equality checking all the required fields.

More Related Contents:

  1. How to receive special character?
  2. jQuery post() with serialize and extra data
  3. Clear Text Selection with JavaScript
  4. Generate HTML table from 2D JavaScript array
  5. Select a complete table with Javascript (to be copied to clipboard)
  6. Access object properties within object [duplicate]
  7. Wait till a Function with animations is finished until running another Function
  8. Throttle amount of promises open at a given time
  9. Why is bind slower than a closure?
  10. Create a file using Javascript in Chrome on client side
  11. Why is document.all falsy?
  12. jQuery selector doesn’t update after dynamically adding new elements
  13. Scroll event firing too many times. I only want it to fire a maximum of, say, once per second
  14. How to convert Set to Array?
  15. Accessing Vuex state when defining Vue-Router routes
  16. Why does String.match( / \d*/ ) return an empty string?
  17. Multiple Windows using window.open()
  18. Scale a div to fit in window but preserve aspect ratio
  19. RXJS Wait for all observables in an array to complete (or error)
  20. Calculating median – javascript
  21. Dynamically change CSS of link based on current page
  22. How to enumerate dates between two dates in Moment
  23. Why does Array.apply(null, [args]) act inconsistently when dealing with sparse arrays?
  24. Why global variable ‘name’ changes to string? [duplicate]
  25. jQuery in Chrome returns “block” instead of “inline”
  26. How do I retrieve if the popstate event comes from back or forward actions with the HTML5 pushstate?
  27. How to write into a file (in user directory) using JavaScript?
  28. Getting HTML elements by their attribute names
  29. Change onClick attribute with javascript
  30. Execute JS code after pressing the spacebar

Leave a Comment