如何在不使用javascript截断编码字符的情况下截断HTML编码文本

I need to write some client-side javascript for a webpage that will truncate the text inside a div, when the onclick event for a button is fired (the purpose of the button is so that users can toggle the displayed text between complete and truncated versions). There won't be any HTML tags in the text, but there may be HTML encoded characters such as " and &I need to write some client-side javascript for