Add Admin JavaScript

It is certainly possible that you can put yourself in an unfortunate position by supplying JavaScript that could render the admin (in whole or in part) inoperable or hidden, making it seeminly impossible to fix or revert your changes. Fortunately, there are a number of approaches you can take to correct the problem. The recommended approach is to visit the URL for the plugin's settings page, but appended with a special query parameter to disable the output of its JavaScript. The plugin's settings page would typically be at a URL like https://example.com/wp-admin/options-general.php?page=add-admin-javascript%2Fadd-admin-javascript.php. Append &c2c-no-js=1 to that, so that the URL is https://example.com/wp-admin/options-general.php?page=add-admin-javascript%2Fadd-admin-javascript.php&c2c-no-js=1 (obviously change example.com with the domain name for your site). There are other approaches you can use, though they require direct database or server filesystem access:

• Disable JavaScript in your browser and revist the page. With JavaScript disabled, any JavaScript defined by the plugin would have no effect for you. Fix the JavaScript you defined and then re-enabled JavaScript for your browser.
• In the site's wp-config.php file, define a constant to disable output of the plugin-defined JavaScript: define( 'C2C_ADD_ADMIN_JAVASCRIPT_DISABLED', true );. You can then visit the site's admin. Just remember to remove that line after you've fixed the JavaScript (or at least change "true" to "false"). This is an alternative to the query parameter approach described above, though it persists while the constant remains defined. There will be an admin notice on the plugin's setting page to alert you to the fact that the constant is defined and effectively disabling the plugin from adding any JavaScript.
• Presuming you know how to directly access the database: within the site's database, find the row with the option_name field value of c2c_add_admin_javascript and delete that row. The settings you saved for the plugin will be deleted and it will be like you've installed the plugin for the first time.
• If your server has WP-CLI installed, you can delete the plugin's setting from the commandline: wp option delete c2c_add_admin_javascript

Yes, via the "Admin JavaScript Files" input field on the plugin's settings page.

No, not presently. At least not directly. By default, the JavaScript is added to every admin page on the site. However, you can preface your selectors with admin page specific class(es) on 'body' tag to ensure CSS only applies on certain admin pages. (e.g. jQuery('body.index-php h2').hide();). Or, you can hook all the plugin's filters and determine the current admin page content to decide whether the respective hook argument should be returned (and thus output) or not.

No, not presently. At least not directly. By default, the JavaScript is added for any user that can enter the admin section of the site. You can hook all the plugin's filters and determine the current user to decide whether the respective hook argument should be returned (and thus output) for the user or not.

The plugin's syntax highlighting of JavaScript (available as of WP 4.9) honors the built-in setting for whether syntax highlighting should be enabled or not. To disable syntax highlighting, go to your profile page. Next to "Syntax Highlighting", click the checkbox labeled "Disable syntax highlighting when editing code". Note that this checkbox disables syntax highlighting throughout the admin interface and not just specifically for the plugin's settings page.

Yes.