Question

If the visible of a server side control is set to false, even I know it’s id, is that possible to know that it is invisible by using jQuery? what code should I use, say the control id=”test1″.

Answer 1

if ($('#test1').is(':hidden')) {...}

Or

if ($('#test1').css('display') == 'none') {...}

• The first uses the jQuery pseudo-selector :hidden: http://api.jquery.com/hidden-selector/
• The second just tests the display property of the element to see if it is set to none (hidden…)

The :hidden pseudo-selector checks the following:

• If the object has a CSS display value of none.
• If it is a form element with type=”hidden”.
• If the element’s width and height are explicitly set to 0.
• If an ancestor element is hidden, so the element is not shown on the page.

If setting the element visible = false on the server-side makes the element not included in the DOM then you can check for the existance of an element with this:

if ($('#test1').length > 0) {..}

.length will return the number of elements found, since we are selecting with an ID we know only one can be returned, so if .length returns zero then the object doesn’t exist and if it returns one then it does.