转义html字符

var htmlspecialchars = function(str) {    if(!str) {        str = '';    }    str = str.replace(/&amp;/g, '&');    str = str.replace(/&lt;/g, '<');    str = str.replace(/&gt;/g, '>');    str = str.replace(/&quot;/g, '"');    str = str.replace(/&#039;/g, "'");    return str;}