how to make an existing listbox autocomplete I have made a content type which has a list box field. now I need to change its widget to autocomplete but as you know list box fields does not have autocomplete widget. now I have added 650 contents of that type and changing the field type would be my last solution because I can't spend time in editing 650 contents!
so is there any way to add an autocomplete widget to the current list box field?
The list box field does not have autocomplete widget unless you use the taxonomy terms, and there are already 650 contents and you do not want to edit the content then you should use the Chosen module, the chosen module will allow you to search within the list. here is the examples page http://harvesthq.github.io/chosen/

following is the module page.
https://www.drupal.org/project/chosen