How can you check for a #hash in a URL using JavaScript?

I have some jQuery/JavaScript code that I want to run only when there is a hash (#) anchor link in a URL. How can you check for this character using JavaScript? I need a simple catch-all test that would detect URLs like these:

• example.com/page.html#anchor
• example.com/page.html#anotheranchor

Basically something along the lines of:

if (thereIsAHashInTheUrl) {
    do this;
} else {
    do this;
}

Simple use of location hash:

if(window.location.hash) {
  // Fragment exists
} else {
  // Fragment doesn't exist
}