jquery: how do I check there is a fragment on the url when I click the browser's back button

I know there are plenty of plugins can archive this, but I think I want to make a simple one for learning purposes because I have come this far that I can change the url with location.hash when I load an ajax page.

Now I only need to find out - how do I use simply jquery to check there is a fragment on the url when I click back button on the browser?

I came across this simple concept but it works only if I ciick the browser refresh button but not the back button,

$(document).ready(function(){    

if(window.location.hash) {

开发者_开发百科    // Fragment exists

    var hash = location.hash;
    alert(hash);

  } else {
    // Fragment doesn't exist
  }

});

Can you please give me some guide?

Thanks.

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You are looking for the hashchange event. But it is not supported the well by older browsers which is why all the plugins exist. Check out the code of Ben Alman's hashchange event plugin to see how it supports all the fun quirks of different browsers:

https://github.com/cowboy/jquery-hashchange/blob/master/jquery.ba-hashchange.js

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JQuery has a means of simulating hashchange event for older browsers too - basically it works by polling the URL. You might also want to think about what you want to do with redirects e.g. for authentication) See http://tshrestha.blogspot.com/2013/05/hash-bang-url-fragments-and-http.html