如果代码中没有< script> 可以尝试（演示）：

  container.innerHTML = container.innerHTML 
 .replace（/<（\ /？）（[^：> \s] *： ）？（[^>] +）> / g，< $ 1 $ 3>）
 

Is there an easy way, for example, to drop an XML name space, but keep the tag as is with jQuery or JavaScript? For example:

<html:a href="#an-example" title="Go to the example">Just an Example</html:a>

And change it to:

<a href="#an-example" title="Go to the example">Just an Example</a>

On the fly with jQuery or JavaScript and not knowing the elements and or attributes inside?

If there is no <script> tag in the code to be replaced you can try (demo):

container.innerHTML = container.innerHTML
                               .replace(/<(\/?)([^:>\s]*:)?([^>]+)>/g, "<$1$3>")