CSS Selector that applies to elements with two classes

Is there a way to select an element with CSS based on the value of the class attribute being set to two specific classes. For example, let's say I have 3 divs:

<div class="foo">Hello Foo</div>
<div class="foo bar">Hello World</div>
<div class="bar">Hello Bar</div>

What CSS could I write to select ONLY the second element in the list, based on the fact that it is a member of both the foo AND bar classes?

Chain both class selectors (without a space in between):

.foo.bar {
    /* Styles for element(s) with foo AND bar classes */
}

---

If you still have to deal with ancient browsers like IE6, be aware that it doesn't read chained class selectors correctly: it'll only read the last class selector (.bar in this case) instead, regardless of what other classes you list.

To illustrate how other browsers and IE6 interpret this, consider this CSS:

* {
    color: black;
}

.foo.bar {
    color: red;
}

Output on supported browsers is:

<div class="foo">Hello Foo</div>       <!-- Not selected, black text [1] -->
<div class="foo bar">Hello World</div> <!-- Selected, red text [2] -->
<div class="bar">Hello Bar</div>       <!-- Not selected, black text [3] -->

Output on IE6 is:

<div class="foo">Hello Foo</div>       <!-- Not selected, black text [1] -->
<div class="foo bar">Hello World</div> <!-- Selected, red text [2] -->
<div class="bar">Hello Bar</div>       <!-- Selected, red text [2] -->

Footnotes:

• Supported browsers:

1. Not selected as this element only has class foo.
2. Selected as this element has both classes foo and bar.
3. Not selected as this element only has class bar.
   
   

• IE6:

1. Not selected as this element doesn't have class bar.
2. Selected as this element has class bar, regardless of any other classes listed.

With SASS:

.foo {
  /* Styles with class "foo" */
  &.bar {
    /* Styles with class "foo bar" */
  }
}

See https://stackoverflow.com/a/49401539/7470360