Answers for "find div by class"

get element by class

var elements = document.getElementsByClassName(names); // or:
var elements = rootElement.getElementsByClassName(names);

jquery find tag and class

$(".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

how to find a name of class from page in jquery

if ($('.Mandatory').length > 0) {
  //do your thing
}

how to find a name of class from page in jquery

$('.Mandatory').each(function(){
  //do your thing
});