JezK
Edit File: set-post-thumbnail.min.js
/*! This file is auto-generated */ window.WPSetAsThumbnail=function(n,t){var a=jQuery("a#wp-post-thumbnail-"+n);a.text(wp.i18n.__("Saving\u2026")),jQuery.post(ajaxurl,{action:"set-post-thumbnail",post_id:post_id,thumbnail_id:n,_ajax_nonce:t,cookie:encodeURIComponent(document.cookie)},function(t){var e=window.dialogArguments||opener||parent||top;a.text(wp.i18n.__("Use as featured image")),"0"==t?alert(wp.i18n.__("Could not set that as the thumbnail image. Try a different attachment.")):(jQuery("a.wp-post-thumbnail").show(),a.text(wp.i18n.__("Done")),a.fadeOut(2e3),e.WPSetThumbnailID(n),e.WPSetThumbnailHTML(t))})};