php - Show textarea or div (just below the comment to reply),when i click reply button on comment system javascript not jquery -

so trying make comment system in new site.all comments have reply button id 'replybtn' which, onclick want show textarea or input field inside div id 'replyform' right below respective comment. , using php,mysql retrieve comments.

<div class='cmt'>     <div class='cmttext'></div>     <div id='replybtn'></div>     <div id='replyform'>        <form method='post' ..... >           <textarea name='reply' ></textarea>           <input type='submit' />        </form>     </div> </div> 

thank you. first question asked on stackoverflow, sorry if have not given sufficient information.

try this. plain javascript. modify below want. :) updated it.

var varhtml = "<form method='post' ..... ><textarea name='reply' ></textarea> <input type='submit' /> </form>";      var allelements = document.body.getelementsbyclassname("replybtn");    var addcommentfield = function() {    (var = 0; allelements.length > i; i++) {      if (allelements[i] === this) {        console.log("this " + i);          if (document.getelementsbyclassname("replyform")[i].innerhtml.length === 0) {          document.getelementsbyclassname("replyform")[i].innerhtml = varhtml;        }        }    }  };      (var = 0; < allelements.length; i++) {    allelements[i].addeventlistener('click', addcommentfield, false);  }

<div class='cmt'>    <div class='cmttext'></div>    <button class='replybtn'>replybtn</button>    <div class='replyform'></div>  </div>  <div class='cmt'>    <div class='cmttext'></div>    <button class='replybtn'>replybtn</button>    <div class='replyform'></div>  </div>  <div class='cmt'>    <div class='cmttext'></div>    <button class='replybtn'>replybtn</button>    <div class='replyform'></div>  </div>