Topic: Disposal of mdb Button instances

Torroni pro asked 3 weeks ago

In my application, I have a Modal which allows the user to specify a custom filter to be applied to an SQL query. The user selects a field, and a JS function automatically adds a Select for the comparison operator (=, !=, <, etc..), an Input or a Select for the value (depending on the field), and a Select for the logical criteria (AND/OR). If the user selects a logical criteria, a JS function dynamically creates another row that contains the same controls: a Select for the Field, a Select for the comparison operator, an Input or a Select for the value (depending on the field), etc... The last control in each row is a "clear" button that deletes all the controls in the row and resets it to its default state. The user can delete a filter row, or change the field, and each time these events are triggered, the JS code needs to remove some DOM elements and re-create them. I have learned that it is not enough to remove an element from the DOM using the standard html API, I also need to dispose the corresponding mdb elements (even though I'm not sure I understand why). I have learned how to dispose the Select and the Input components, but I don't know if I have to dispose also the Button components, and if I do I don't know how to do it. According to the API documentation, there is a dispose method, but if I select the element with a query selector and then call dispose, I get an error:

"Uncaught TypeError: Cannot read properties of null (reading 'dispose')"

This is the code:

var clearElements = itemRow.querySelectorAll("[id*='ButtonClear']");
if (clearElements.length > 0) {

I have a few questions: 1 - do I always have to dispose an mdb component before removing from the DOM or only in some circumstances, for example if I need to re-create it dynamically or if create a different DOM element with the same id as the old deleted element 2 - If the answer to the first question is yes, do I need to dispose also dynamically created Button elements? If yes, what is the syntax? 3 - what exactly happens if I don't call dispose before removing the element from the DOM and re-creating it? Is it "just" a memory leak, i.e. new objects will be continually created but never destroyed? Or I will have a problem if I dynamically create a new element with the same id as the old element? I attach a screenshot of the Modal, in case it is not clear from my textual description: enter image description here

kpienkowska staff answered 1 week ago

  1. Removing instances is not mandatory for all components but it is a good practice. It may lead to memory leaks if you then proceed to e.g. create a new element with the same ID your browser will remember the previous component, its state, listeners, etc.
  2. Here is a snippet that shows how to dispose button: - but buttons are not auto-initiated unless you add data-mdb-toggle="button" to them in the HTML. So if you didn't do that or didn't initiate it with JS there is no instance to be disposed of.

Torroni pro commented 1 week ago

Thank you for the explanation, it is clear now.

Please insert min. 20 characters.


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Specification of the issue

  • User: Pro
  • Premium support: No
  • Technology: MDB Standard
  • MDB Version: MDB5 6.1.0
  • Device: laptop
  • Browser: Brave Browser Version 1.48.167 Chromium: 110.0.5481.104 (Official Build) (64-bit)
  • OS: Windows 10 Enterprise 22H2
  • Provided sample code: No
  • Provided link: No