replace specific tag name javascript

You can't change the tag name of an existing DOM element; instead, you have to create a replacement and then insert it where the element was.

The basics of this are to move the child nodes into the replacement and similarly to copy the attributes. So for instance:

var wns = document.getElementById("93");
var lmn = document.createElement("lmn");
var index;

// Copy the children
while (wns.firstChild) {
    lmn.appendChild(wns.firstChild); // *Moves* the child
}

// Copy the attributes
for (index = wns.attributes.length - 1; index >= 0; --index) {
    lmn.attributes.setNamedItem(wns.attributes[index].cloneNode());
}

// Replace it
wns.parentNode.replaceChild(lmn, wns);

Live Example: (I used div and p rather than wns and lmn, and styled them via a stylesheet with borders so you can see the change)

document.getElementById("theSpan").addEventListener("click", function() {
  alert("Span clicked");
}, false);

document.getElementById("theButton").addEventListener("click", function() {

  var wns = document.getElementById("target");
  var lmn = document.createElement("p");
  var index;

  // Copy the children
  while (wns.firstChild) {
    lmn.appendChild(wns.firstChild); // *Moves* the child
  }

  // Copy the attributes
  for (index = wns.attributes.length - 1; index >= 0; --index) {
    lmn.attributes.setNamedItem(wns.attributes[index].cloneNode());
  }

  // Insert it
  wns.parentNode.replaceChild(lmn, wns);
}, false);

div {
  border: 1px solid green;
}
p {
  border: 1px solid blue;
}

<div id="target" foo="bar" onclick="alert('hi there')">
  Content before
  <span id="theSpan">span in the middle</span>
  Content after
</div>
<input type="button" id="theButton" value="Click Me">

See this gist for a reusable function.

Side note: I would avoid using id values that are all digits. Although they're valid in HTML (as of HTML5), they're invalid in CSS and thus you can't style those elements, or use libraries like jQuery that use CSS selectors to interact with them.

There are several problems with your code:

1. HTML element IDs must start with an alphabetic character.
2. document.getElementById("99").replace(/wns/g,"lmn") is effectively running a replace command on an element. Replace is a string method so this causes an error.
3. You're trying to assign this result to document.getElementById("99").innerHTML, which is the HTML inside the element (the tags, attributes and all are part of the outerHTML).
4. You can't change an element's tagname dynamically, since it fundamentally changes it's nature. Imagine changing a textarea to a select… There are so many attributes that are exclusive to one, illegal in the other: the system cannot work!

What you can do though, is create a new element, and give it all the properties of the old element, then replace it:

<wns id="e93" onclick="wish(id)">
    ...
</wns>

Using the following script:

// Grab the original element
var original    = document.getElementById('e93');
// Create a replacement tag of the desired type
var replacement = document.createElement('lmn');

// Grab all of the original's attributes, and pass them to the replacement
for(var i = 0, l = original.attributes.length; i < l; ++i){
    var nodeName  = original.attributes.item(i).nodeName;
    var nodeValue = original.attributes.item(i).nodeValue;

    replacement.setAttribute(nodeName, nodeValue);
}

// Persist contents
replacement.innerHTML = original.innerHTML;

// Switch!
original.parentNode.replaceChild(replacement, original);

Demo here: http://jsfiddle.net/barney/kDjuf/

You can replace the whole tag using jQuery

var element = $('#99');
element.replaceWith($(`<lmn id="${element.attr('id')}">${element.html()}</lmn>`));

You can achieve this by using JavaScript or jQuery.

We can delete the DOM Element(tag in this case) and recreate using .html or .append menthods in jQuery.

$("#div-name").html("<mytag>Content here</mytag>");

OR

$("<mytag>Content here</mytag>").appendTo("#div-name");