alirezas

function fadeOut(el){
  el.style.opacity = 1;

  (function fade() {
    if ((el.style.opacity -= .1) < 0) {
      el.style.display = "none";
    } else {
      requestAnimationFrame(fade);
    }
  })();

azizultex

Best way to override a plugin function is to use mu-plugins (Must Use Plugins)
https://gregrickaby.com/2013/10/create-mu-plugin-for-wordpress/#comment-14420

Aleternatively, follow below :

1. Copy the plugin shortcode function and put it anywhere in Child Theme and rename it like custom_cs_user_login_shortcode.
2. use 'wp_head' action to remove the plugin shortcode and register the new shortcode again with the new function name like custom_cs_user_login_shortcode. 


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