jQuery essential tips

• Check existence of an attribute :if ($('#id').attr('attributo') !== undefined) {
// attribute exists
} NOTE: id attribute is never undefined, but equal to ""


• Check existence of an element :if ($('#id').length > 0) {
// element exists
}


• Show/Hide image ajax loading :html :
  
  
  
  
  
  javascript:
  $(document).ready(function(){
  $('#loadingimg').ajaxStart(function() {
  $(this).show();
  }).ajaxStop(function() {
  $(this).hide();
  });
  }