Question

(function (){

    var num = parseInt($('body').attr('data-site')) + 1,
        theul = $(".submenu li:nth-child(" + num + ") a"),
        newNum = num - 1,
        theNewUl = $(".submenu li:nth-child(" + newNum + ") a");

        console.log(theul);
        theul.addClass('activex');
        console.log(theNewUl);
        theNewUl.addClass('lastsl');

})();

Hello, when I try to run this script console says:

“Uncaught Syntax error, unrecognized expression: li:nth-child”

Althoung I linked the jQuery source before this script,

thanks for anwsers

Answer 1

1. You can use .data("foo") in favor of .attr("data-foo").
2. You can use the :eq() selector. It’s zero-based, which is what you seem to want.
3. You do not need to call .addClass() on a separate line.
4. You must use the radix 10 when you use parseInt(), or numbers like 08 will be interpreted as octal.
5. You need to make sure that num actually contains a number, or parseInt() will return NaN and that will break your following code.
6. Prefix variables that contain a jQuery object with a $. It’s a useful convention to follow.

Try:

var num = parseInt($('body').data("site"), 10),
    $theul = $(".submenu li:eq(" + num + ") a").addClass('activex'),
    $theNewUl = $(".submenu li:eq(" + (num-1) + ") a").addClass('lastsl');