I want to change placeholder of a dropdown created by selectize.js when the parent dropdown changes its selection to load the options of the dropdown whose placeholder to be cha
selectize.js will create an input below the select. This input will have the class .selectize-control.
You can replace the placeholder of this input field with jQuery.
You can do something like:
$(".selectize-control").attr('placeholder','Hello World!');
If you would like a working example, Ill need more information about your code.