Q:

Hashing element contents in-place with Crypto-js

I am trying to hash data using JavaScript. When I run the first code it will hash using document.write. Now I try the second code to hash by content id it didn't work. Can anyone explain why?
<script src="http://crypto-js.googlecode.com/svn/tags/3.1.2/build/rollups/sha256.js"></script>
<script>
    var hash = CryptoJS.SHA256("hello");
    document.write(hash.toString(CryptoJS.enc.Hex));
</script>

using this first method will work very fine
2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824 
<script>
    var hash = CryptoJS.SHA256;
    var it = (hash.toString(CryptoJS.enc.Hex));
    document.getElementById('hashit').innerHTML = 'it';
</script>

<p id="hashit">Hello</p>

A:

If you want to hash something in-place in an element then you need to read out the value/text, hash it and write the text back:
var element = document.getElementById('hashit');
var hash = CryptoJS.SHA256(element.innerHTML);
element.innerHTML = hash.toString();

Here is a runnable snippet which changes the value after 2 seconds.

setTimeout(function(){
  var element = document.getElementById('hashit');
  var hash = CryptoJS.SHA256(element.innerHTML);
  element.innerHTML = hash.toString();
}, 2000);
<script src="https://cdn.rawgit.com/CryptoStore/crypto-js/3.1.2/build/rollups/sha256.js"></script>
<p id="hashit">Hello</p>

Keep in mind that JavaScript is not like PHP. You can't simply use variables in strings like this element.innerHTML = 'it';. You have to  useelement.innerHTML = it;.

