jQuery How to control, does an element exist in document?

Question

I want to control does an element exist in document with its ID, when page is loading. I tried code which is below, but i failed.

   if($(':not(#<%=TextBox1.ClientID %>)')){
     alert("Object is null")else{alert("Object is exist")}}

Thansk for your helps already now.

Answer 1

Read from this post (courtesy of jakemcgraw):

Is there an "exists" function for jQuery?

jQuery.fn.exists = function(){return jQuery(this).length>0;}

if ($('#<%=TextBox1.ClientID %>').exists()) {
    // Do something
}

Answer 2

I just use directly the length property, as suggested on the jQuery FAQ:

if ($('#<%=TextBox1.ClientID %>').length) {
    // Do something
}