//document.getElementById()的简写形式 模仿jquery
function $() {
    var elements = new Array();
    for (var i = 0; i < arguments.length; i++) {
        var element = arguments[i];
        if (typeof element == 'string') {
            element = document.getElementById (element);
        }
        if (arguments.length == 1) {
            return element;
        }
        elements.push (element);
    }
    return elements;
}