Today after updating my site to latest WordPress  version 4.5. i came along this issue. My customizer  preview init is totally blank with no section and panel. Along with i got this error on console

Uncaught TypeError: data.defaultValue.substring is not a function

How i solved this issue?

  • First I deactivated all plugin installed on a site to see if plugin is creating issue.
  • Then I dequeue  all the scripts from functions.php as well from customizer file where theme had added for creating customizer setting. To make sure which file is creating conflict i tried by removing file sequentially that is added on functions.php
  • After I found that the file where customizer setting for control,setting, panel and section is causing the problem.
  • Then to know if setting id is creating conflict i tried by changing all section id to different value then tracking one by one.
  • Finally I found setting id “widget_titles” is creating problems and changed to some XXXX id which solve the issue

After debugging for 3 hour finally i found the solution of the problems.

Conclusion: Always name options id,setting id and  , functions  prefixing with theme or plugin slug. It will prevents your id conflicting to other third party or WordPress core itself.


Sushil Adhikari


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  1. Hi Vaibhav Kumar,

    I just gone through your site and found that there is no any js conflict. You just check if your customizer id is conflicting to default WordPress options id.

    To know which options is making conflict , first try by deactivating all section manaually. After you detect the section then go for disabling every customizer setting.

    In this way you can find conflicting id and then change that id to any other id prefixing with your theme or plugin domain.

    Note: Be sure you had include customizer file on functions.php.

    Let me know how it will goes.

    Sushil Adhikari


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