问题:

I'm trying to find an option's index.

For example, I would like to get 1 when I run the following fake code

JS:

$("#test[value='USD']").index() ?

HTML:

<select id='test'>
  <option value='CNY'>CNY</option>
  <option value='USD'>USD</option>
</select>

is this possible?

回答1:

You were very close, you want to use index on the option element, not the select:

var i = $("#test option[value='USD']").index();

Gratuitous live example

Note that this will break if your select contains optgroup elements. If so, you'll want to pass 'option' into index:

var i = $("#test option[value='USD']").index('option');

Live example (I changed the position so it's the 4th element for that example)

回答2:

from Reference

.index() can take a DOM node and returns an index, 
 We get back the zero-based position of the list item:

回答3:

Im sure there is a straight forward way of counting the index in such occasions i just can't remember it right now, but you could try creating a function that loops between each values, and raises a counter +1 each time, until you get $("#test").val("USD")