jquery find

$( "li.item-a" )
  .closest( "ul" )
  .css( "background-color", "red" );

$(this).children('div').show();

{
    'name': $(this).children('input[name="paramName"]').val(),
    'value': $(this).children('input[name="paramPrice"]').val()
};

var myVar = $("#start").find('.myClass').val();

$(".txtClass")                  =>  getElementsByClassName()

$("#childDiv2 .txtClass")       =>  getElementById(),
                                    then getElementsByClassName()

$("#childDiv2 > .txtClass")     =>  getElementById(),
                                    then iterate over children and check class

$("input.txtClass")             =>  getElementsByTagName(),
                                    then iterate over results and check class

$("#childDiv2 input.txtClass")  =>  getElementById(),
                                    then getElementsByTagName(),
                                    then iterate over results and check class

$( "li.item-ii" ).find( "li" ).css( "background-color", "red" );