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

  if(window.location.hash) {
      var hash = window.location.hash.substring(1); //Puts hash in variable, and removes the # character
      alert (hash);
      // hash found
  } else {
      // No hash found
  }

Put the following:

<script type="text/javascript">
    if (location.href.indexOf("#") != -1) {
        // Your code in here accessing the string like this
        // location.href.substr(location.href.indexOf("#"))
    }
</script>

If the URI is not the document's location this snippet will do what you want.

var url = 'example.com/page.html#anchor',
    hash = url.split('#')[1];

if (hash) {
    alert(hash)
} else {
    // do something else
}

Have you tried this?

if (url.indexOf('#') !== -1) {
    // Url contains a #
}

(Where url is the URL you want to check, obviously.)

$('#myanchor').click(function(){
    window.location.hash = "myanchor"; //set hash
    return false; //disables browser anchor jump behavior
});
$(window).bind('hashchange', function () { //detect hash change
    var hash = window.location.hash.slice(1); //hash to string (= "myanchor")
    //do sth here, hell yeah!
});

This will solve the problem ;)

window.location.hash 

will return the hash identifier

...or there's a jquery selector:

$('a[href^="#"]')

You can parse urls using modern JS:

var my_url = new URL('http://www.google.sk/foo?boo=123#baz');

my_url.hash; // outputs "#baz"
my_url.pathname; // outputs "/moo"
​my_url.protocol; // "http:"
​my_url.search; // outputs "?doo=123"

urls with no hash will return empty string.

Here's what you can do to periodically check for a change of hash, and then call a function to process the hash value.

var hash = false; 
checkHash();

function checkHash(){ 
    if(window.location.hash != hash) { 
        hash = window.location.hash; 
        processHash(hash); 
    } t=setTimeout("checkHash()",400); 
}

function processHash(hash){
    alert(hash);
}

var requestedHash = ((window.location.hash.substring(1).split("#",1))+"?").split("?",1);

Most people are aware of the URL properties in document.location. That's great if you're only interested in the current page. But the question was about being able to parse anchors on a page not the page itself.

What most people seem to miss is that those same URL properties are also available to anchor elements:

// To process anchors on click    
jQuery('a').click(function () {
   if (this.hash) {
      // Clicked anchor has a hash
   } else {
      // Clicked anchor does not have a hash
   }
});

// To process anchors without waiting for an event
jQuery('a').each(function () {
   if (this.hash) {
      // Current anchor has a hash
   } else {
      // Current anchor does not have a hash
   }
});

function getHash() {
  if (window.location.hash) {
    var hash = window.location.hash.substring(1);

    if (hash.length === 0) { 
      return false;
    } else { 
      return hash; 
    }
  } else { 
    return false; 
  }
}

Partridge and Gareths comments above are great. They deserve a separate answer. Apparently, hash and search properties are available on any html Link object:

<a id="test" href="foo.html?bar#quz">test</a>
<script type="text/javascript">
   alert(document.getElementById('test').search); //bar
   alert(document.getElementById('test').hash); //quz
</script>

Or

<a href="bar.html?foo" onclick="alert(this.search)">SAY FOO</a>

Should you need this on a regular string variable and happen to have jQuery around, this should work:

var mylink = "foo.html?bar#quz";

if ($('<a href="'+mylink+'">').get(0).search=='bar')) {
    // do stuff
}

(but its maybe a bit overdone .. )

Throwing this in here as a method for abstracting location properties from arbitrary URI-like strings. Although window.location instanceof Location is true, any attempt to invoke Location will tell you that it's an illegal constructor. You can still get to things like hash, query, protocol etc by setting your string as the href property of a DOM anchor element, which will then share all the address properties with window.location.

Simplest way of doing this is:

var a = document.createElement('a');
a.href = string;

string.hash;

For convenience, I wrote a little library that utilises this to replace the native Location constructor with one that will take strings and produce window.location-like objects: Location.js

I noticed that all of these answers mostly check window.location.hash and make it difficult to write tests.

 const hasHash = string => string.includes('#')

You can also remove the hash from a url like so:

const removeHash = string => {
 const [url] = string.split('#')
 return url
}

And finally you can combine the logic together:

if(hasHash(url)) {
 url = removeHash(url)
}

Usually clicks go first than location changes, so after a click is a good idea to setTimeOut to get updated window.location.hash

$(".nav").click(function(){
    setTimeout(function(){
        updatedHash = location.hash
    },100);
});

or you can listen location with:

window.onhashchange = function(evt){
   updatedHash = "#" + evt.newURL.split("#")[1]
};

I wrote a jQuery plugin that does something like what you want to do.

It's a simple anchor router.

Here is a simple function that returns true or false (has / doesn't have a hashtag):

var urlToCheck = 'http://www.domain.com/#hashtag';

function hasHashtag(url) {
    return (url.indexOf("#") != -1) ? true : false;
}

// Condition
if(hasHashtag(urlToCheck)) {
    // Do something if has
}
else {
    // Do something if doesn't
}

Returns true in this case.

Based on @jon-skeet's comment.

This is a simple way to test this for the current page URL:

  function checkHash(){
      return (location.hash ? true : false);
  }

Modern way, we can now safely in 2024 use the browser built-in URL api, who provides many tools for URL parsing.

Inspect the URL Object:

console.log( new URL(location) )

Get the URL hash:

new URL(location).hash

https://caniuse.com/url

Use :

var hash = window.location.hash;

var hash = hash.replace('#', '');

then the variable "hash" has the hash without "#"

sometimes you get the full query string such as "#anchorlink?firstname=mark"

this is my script to get the hash value:

var hashId = window.location.hash;
hashId = hashId.match(/#[^?&\/]*/g);

returns -> #anchorlink