jQuery - how to test if selector matches anything?

问题:

Say I have the following:

$('#foo')

I'd like to know if that selector matches anything. How do I test for this?

回答1:

if ($('#foo').length > 0) {

    // do things
}

should do it

回答2:

Use a Javascript Console to see what your method call returns. Type your command into the console, and then hit enter.

Shortcuts to open a JS console:

• Chrome: Ctrl + Shift + I, then click the Console tab
• Firefox: Ctrl + Shift + J