title: Positive lookahead with javascript regex
body: <p>I have been messed up with regex.. I found it difficult for me..I have seen a code like:</p>
  
  <pre><code>function myFunction() {
     var str = "Is this all there is";
     var patt1 = /is(?= all)/;
     var result = str.match(patt1);
     document.getElementById("demo").innerHTML = result;
  }
  </code></pre>
  
  <p>When i run this code it gave me the output <code>is</code>.</p>
  
  <p>But when i add like <code>/is(?=there)/</code> it didnt output anything. I am new to regular expression ..hope you guys  can help in in understanding positive lookahead in regex..I have followed many tutorials it didnt helped me.</p>
  
  <p>Hope you guys can help me out. Thanks!</p>