转义html字符

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