可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试):

问题:

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?

回答1:

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 →.

回答2:

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

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

回答3:

<!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>.