（ document ）。ready（ function （）{

（ tr）。hover（ function （）{

（ this ）。css（ background-color， red）;
}， function （）{

Hello,


Why is this working just fine:

jQuery(document).bind('keydown', function (evt) {
        if (evt.keyCode == 38) {
            var element = document.getElementById("table_row_2");
            element.style.backgroundColor = "red";
        }
    });

But this isn't working:

jQuery(document).bind('keydown', function (evt) {
        if (evt.keyCode == 38) {
            var element = document.getElementById("table_row_2");
            element.css("background-color","red");
        }
    });

What I have tried:

while this again works just fine:

<pre lang="text">$(document).ready(function () {
        $("tr").hover(function () {
            $(this).css("background-color", "red");
        }, function () {
            $(this).css("background-color", "red");
        });
    });

Im confused...

(document).ready(function () {

("tr").hover(function () {

(this).css("background-color", "red"); }, function () {