JSFiddle - React, Tailwind, and code Playground

HTML

<html>
<body>
   <p>Set the variable to different value and then try...</p>
</body>
</html>

JavaScript

function addBook(book){
  if( book == "history" ){
      document.write("<b>History Book</b>");
  }else if( -1 != ["maths", "mathematics","arithmetics"].indexOf(book.toLowerCase()) ){
      document.write("<b>Maths Book</b>");
  }else{
     document.write("<b>Unknown Book</b>");
  }
}

addBook("Maths");
addBook("mathematics");
addBook("Arithmetics");