Alt attribute encoding with JavaScript

Html entities must be encoded in alt attribute of an image in HTML page. So

<img id="formula" alt="A &rarr; B" src="formula.png" />

will work well.

On the other hand, the same JavaScript code will not work

document.getElementById('formula').alt = 'A &rarr; B';

and will produce A → B instead of A → B.

How to do it through JavaScript, when it is not possible to put the special (unencoded) characters in the source code?

Here's an alternative if you can't save your file using a Unicode format:

function decodeHTML(str) {
    return str.replace(/&#(\d+);?/g, function() {
        return String.fromCharCode(arguments[1])
    });
}

However, this requires you to use the numeric representation. In this case →.

JavaScript has its own system for escaping special characters in strings:

document.getElementById('formula').alt = 'A \u2192 B';

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>Decode HTML entities using JavaScript</title>
  </head>
  <body>
    <img id="formula" src="vote-arrow-up-on.png" alt="A &rarr; C">
    <script>
      function html_entity_decode(str) {
        var p = document.createElement("p");
        p.innerHTML = str.replace(/</g,"&lt;").replace(/>/g,"&gt;");
        return p.innerHTML;
      }

      var theValue = html_entity_decode('A &rarr; B');
      document.getElementById('formula').title = theValue;
    </script>
  </body>
</html>

Credits to The JavaScript Source.

EDIT: I changed the original code to only use innerHTML on a <p> element, instead of innerHTML and value of a <textarea>.

In that particular case, you don't have encode special HTML characters in JavaScript.

The W3C validator should not complain about this (just tested it) and the document should validate. If not post your code and I'll update my answer.

来源：https://stackoverflow.com/questions/2775328/alt-attribute-encoding-with-javascript

标签

javascript

special-characters

encode

html