JSFiddle - React, Tailwind, and code Playground

HTML

<p class="one">2. April 1507  in Plessis-les-Tours in Frankreich</p>

JavaScript

var myString = $('.one').html();
//alert(myString);

//alert(ary[0] + 'ist 0' + ary[1] + 'ist 1');

var index = myString.indexOf("in");  
var first = myString.substr(0, index); // Gets the first part
var second = myString.substr(index); //Gets second part

alert(first);
alert(second);


$( ".one" ).add( "span" ).html();
$(".one").html("<span>"+first + "</span><br><br>" + arr[1]+"/"+arr[2]);