Is there a way to tell if an end user will be able to handle <a href=“mailto:###”> links?

Question

我正在尝试适应用户未安装电子邮件客户端的情况（例如在我的情况下：我使用Opera的内部邮件客户端，因此，如果我单击mailto：链接，则Internet Explorer不会显示任何内容。） ）

Answer 1

At the moment it is not possible. The closest thing to an answer I ended up with this:

<a id="mail-link" href="mailto:the@email.it" onclick="if (this.hasAttribute('data-clickedonce')) {this.setAttribute('href','mailform.php?to=the@email.it');} this.setAttribute('data-clickedonce','yes');">Send a Mail</a>

The script embedded in the a tag changes the href on the second press. The theory is: if the user has no way to handle the mail protocol, nothing happens and he/she will certainly try to click the link another time.