how to check if page is loaded in jquery code example

Example 1: check if jquery is loaded

$(document).ready(function(){
  if (jQuery) {  
    // jQuery is loaded  
    alert("Yeah!");
  } else {
    // jQuery is not loaded
    alert("Doesn't Work");
  }
});

Example 2: jquery check if document loaded

jQuery offers several ways to attach a function that will run when the DOM is ready. All of the following syntaxes are equivalent:

$( handler )
$( document ).ready( handler )
$( "document" ).ready( handler )
$( "img" ).ready( handler )
$().ready( handler )