在ASP.NET和jQuery中定位服务器控件

Question

I am not able to find the answer in already created threads. Is

$(<%=txtRating.ClientID%>).val("Set the value");

equivalent to

$("#<%=txtRating.ClientID%>").val("Set the value");

? Both are working just fine, so is there any difference? Thank you.

Answer 1

Both work because the browser is automatically creating a variable for each tag id in order to follow HTML5 standard. See http://2ality.com/2012/08/ids-are-global.html

Your code:

$(<%=txtRating.ClientID%>).val("Set the value");
$("#<%=txtRating.ClientID%>").val("Set the value2");

Renders this Javascript on the resulting HTML page:

$(txtRating).val("Set the value");
$("#txtRating").val("Set the value2");

The first one works because:

The HTML5 standard specifies that the window object must have a property key whose value is elem if there is exactly one DOM element elem whose property id has the value key.

For example, given this HTML:

<div id="foo"></div>

You can get the HTML tag by using the id as a variable. Hence $(foo) returns jQuery object for that tag. Same as $('#foo') that also returns jQuery object for same tag.

> "foo" in window
true

> foo
<div id=​"foo">​</div>​

> $(foo)
Object [ <div#foo> ]

> $('#foo')
Object [ <div#foo> ]