我试图在我的一个cutsom页面模板中加入视差效果。js函数在firebug控制台中返回以下错误：

TypeError: $ is not a function

var parallaxElements = $(\'.parallax\'),

    var parallaxElements = $(\'.parallax\'),
        parallaxQuantity = parallaxElements.length;

    $(window).on(\'scroll\', function () {

    window.requestAnimationFrame(function () {

    for (var i = 0; i < parallaxQuantity; i++) {
        var currentElement =  parallaxElements.eq(i);
        var scrolled = $(window).scrollTop();

        currentElement.css({
        \'transform\': \'translate3d(0,\' + scrolled * -0.3 + \'px, 0)\'
        });

    }
});

});