js中html实体字符转义和反转义

function html_encode(str) 
    { 
        var s = ""; 
        if (str.length == 0) return ""; 
        s = str.replace(/&/g, "&"); 
        s = s.replace(/</g, "&lt;"); 
        s = s.replace(/>/g, "&gt;"); 
        s = s.replace(/ /g, "&nbsp;"); 
        s = s.replace(/\'/g, "&#39;"); 
        s = s.replace(/\"/g, "&quot;"); 
            s = s.replace(/\n/g, "<br/>"); 
        return s; 
    } 

    function html_decode(str) 
    { 
        var s = ""; 
        if (str.length == 0) return ""; 
        s = str.replace(/&amp;/g, "&"); 
        s = s.replace(/&lt;/g, "<"); 
        s = s.replace(/&gt;/g, ">"); 
        s = s.replace(/&nbsp;/g, " "); 
        s = s.replace(/&#39;/g, "\'"); 
        s = s.replace(/&quot;/g, "\""); 
        s = s.replace(/<br\/>/g, "\n"); 
        return s; 
    }