How to check if an element DOM exists

Be careful when you wish if an element DOM exists. If you use:

if ( $("#my-id") ){
  // exists?
}

This method doesn’t work because jQuery will return an [Object object] even if the element doesn’t exist. We may use a couple of methods to be sure that an element exists:

if ( $("#my-id").length > 0){
  // ok, exists
}

// or

if ( $("#my-id").length ){
  // ok, exists
}

// or

if ($("#my-id").size() ) {
  // ok, exists
}

// or

if ($("#my-id")[0] ) {
  // ok, extsts
}

How to get jQuery version

$().jquery;
// or
jQuery.fn.jquery;

How to fire an event

// For example, add an event
$('#bottone').click(
  function() {
    alert( 'Hello...' );
  }
);

// Direct fire
$('#bottone').click();

// or
$('#bottone').trigger('click');