jQuery - unrecognized expression: :nth-child -

i trying select :nth-child using jquery, show syntax error.

error: syntax error, unrecognized expression: :nth-child 

here code

var i; jquery('#' + id + ' .tab-pane').each(function (id, t) {     var n = jquery(this).attr('id', 'pane-' + t);     var p_id = n.attr('id');     jquery('#' + id + ' .nav-tabs li:nth-child(' + + ') a').attr('href', p_id);     i++; }); 

please check code missing here

on first iteration, there no value i. query looks this:

jquery('#' + id + ' .nav-tabs li:nth-child(undefined) a').attr('href', p_id); 

on following iterations, undefined++, nan, still won't work.

this won't work. solution set i 1 (or whatever value necesary) on first loop:

var = 1;