JSFiddle - React, Tailwind, and code Playground

JavaScript

var userinput = '<div id="c16430" style="color:red;" class="css-btn">';
            
var pattern = /^[a-zA-Z0-9.;:|_-]+="[a-zA-Z0-9.;:_-]+\"/;
  
userinput = userinput.replace( pattern, "Replaced..." );
  
alert(userinput);