How to decode HTML entities using jQuery?

How to decode HTML entities using jQuery?

How do I use jQuery to decode HTML entities in a string?

Solutions/Answers:

Solution 1:

Security note: using this answer (preserved in its original form below) may introduce an XSS vulnerability into your application. You should not use this answer. Read lucascaro’s answer for an explanation of the vulnerabilities in this answer, and use the approach from either that answer or Mark Amery’s answer instead.

Actually, try

var decoded = $("<div/>").html(encodedStr).text();

Solution 2:

Without any jQuery:

function decodeEntities(encodedString) {
  var textArea = document.createElement('textarea');
  textArea.innerHTML = encodedString;
  return textArea.value;
}

console.log(decodeEntities('1 &amp; 2')); // '1 & 2'

This works similarly to the accepted answer, but is safe to use with untrusted user input.


Security issues in similar approaches

As noted by Mike Samuel, doing this with a <div> instead of a <textarea> with untrusted user input is an XSS vulnerability, even if the <div> is never added to the DOM:

function decodeEntities(encodedString) {
  var div = document.createElement('div');
  div.innerHTML = encodedString;
  return div.textContent;
}

// Shows an alert
decodeEntities('<img src="nonexistent_image" onerror="alert(1337)">')

However, this attack is not possible against a <textarea> because there are no HTML elements that are permitted content of a <textarea>. Consequently, any HTML tags still present in the ‘encoded’ string will be automatically entity-encoded by the browser.

function decodeEntities(encodedString) {
    var textArea = document.createElement('textarea');
    textArea.innerHTML = encodedString;
    return textArea.value;
}

// Safe, and returns the correct answer
console.log(decodeEntities('<img src="nonexistent_image" onerror="alert(1337)">'))

Warning: Doing this using jQuery’s .html() and .val() methods instead of using .innerHTML and .value is also insecure* for some versions of jQuery, even when using a textarea. This is because older versions of jQuery would deliberately and explicitly evaluate scripts contained in the string passed to .html(). Hence code like this shows an alert in jQuery 1.8:

//<!-- CDATA
// Shows alert
$("<textarea>")
.html("<script>alert(1337);</script>")
.text();

//-->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.2.3/jquery.min.js"></script>

* Thanks to Eru Penkman for catching this vulnerability.

Solution 3:

Like Mike Samuel said, don’t use jQuery.html().text() to decode html entities as it’s unsafe.

Instead, use a template renderer like Mustache.js or decodeEntities from @VyvIT’s comment.

Underscore.js utility-belt library comes with escape and unescape methods, but they are not safe for user input:

_.escape(string)

_.unescape(string)

Solution 4:

I think you’re confusing the text and HTML methods. Look at this example, if you use an element’s inner HTML as text, you’ll get decoded HTML tags (second button). But if you use them as HTML, you’ll get the HTML formatted view (first button).

<div id="myDiv">
    here is a <b>HTML</b> content.
</div>
<br />
<input value="Write as HTML" type="button" onclick="javascript:$('#resultDiv').html($('#myDiv').html());" />
&nbsp;&nbsp;
<input value="Write as Text" type="button" onclick="javascript:$('#resultDiv').text($('#myDiv').html());" />
<br /><br />
<div id="resultDiv">
    Results here !
</div>

First button writes : here is a HTML content.

Second button writes : here is a <B>HTML</B> content.

By the way, you can see a plug-in that I found in jQuery plugin – HTML decode and encode that encodes and decodes HTML strings.

Solution 5:

The question is limited by ‘with jQuery’ but it might help some to know that the jQuery code given in the best answer here does the following underneath…this works with or without jQuery:

function decodeEntities(input) {
  var y = document.createElement('textarea');
  y.innerHTML = input;
  return y.value;
}

Solution 6:

You can use the he library, available from https://github.com/mathiasbynens/he

Example:

console.log(he.decode("J&#246;rg &amp J&#xFC;rgen rocked to &amp; fro "));
// Logs "Jörg & Jürgen rocked to & fro"

I challenged the library’s author on the question of whether there was any reason to use this library in clientside code in favour of the <textarea> hack provided in other answers here and elsewhere. He provided a few possible justifications:

  • If you’re using node.js serverside, using a library for HTML encoding/decoding gives you a single solution that works both clientside and serverside.

  • Some browsers’ entity decoding algorithms have bugs or are missing support for some named character references. For example, Internet Explorer will both decode and render non-breaking spaces (&nbsp;) correctly but report them as ordinary spaces instead of non-breaking ones via a DOM element’s innerText property, breaking the <textarea> hack (albeit only in a minor way). Additionally, IE 8 and 9 simply don’t support any of the new named character references added in HTML 5. The author of he also hosts a test of named character reference support at http://mathias.html5.org/tests/html/named-character-references/. In IE 8, it reports over one thousand errors.

    If you want to be insulated from browser bugs related to entity decoding and/or be able to handle the full range of named character references, you can’t get away with the <textarea> hack; you’ll need a library like he.

  • He just darn well feels like doing things this way is less hacky.