Retrieve specific hash tag's value from url

Question

In raw Javascript, how would one go about checking that a specific hash tag exists in a url, then grab the value?

Example: http://www.example.com/index.html#hashtag1

Answer 1

    var HashSearch = new function () {
       var params;

       this.set = function (key, value) {
          params[key] = value;
          this.push();
       };

       this.remove = function (key, value) {
          delete params[key];
          this.push();
       };


       this.get = function (key, value) {
           return params[key];
       };

       this.keyExists = function (key) {
           return params.hasOwnProperty(key);
       };

       this.push= function () {
           var hashBuilder = [], key, value;

           for(key in params) if (params.hasOwnProperty(key)) {
               key = escape(key), value = escape(params[key]); // escape(undefined) == "undefined"
               hashBuilder.push(key + ( (value !== "undefined") ? '=' + value : "" ));
           }

           window.location.hash = hashBuilder.join("&");
       };

       (this.load = function () {
           params = {}
           var hashStr = window.location.hash, hashArray, keyVal
           hashStr = hashStr.substring(1, hashStr.length);
           hashArray = hashStr.split('&');

           for(var i = 0; i < hashArray.length; i++) {
               keyVal = hashArray[i].split('=');
               params[unescape(keyVal[0])] = (typeof keyVal[1] != "undefined") ? unescape(keyVal[1]) : keyVal[1];
           }
       })();
    }

Using it:

Check if a "hash key" is present:

 HashSearch.keyExists("thekey");

Get the value for a hash key:

 HashSearch.get('thekey');

Set the value for a hash key, and update the URL hash:

 HashSearch.set('thekey', 'hey');

Remove a hash key from the URL:

 HashSearch.remove('thekey');

Reload the hash into the local object:

 HashSearch.load();

Push the current key value set to the URL hash:

 HashSearch.push();

Note that when a key does not exist and you try to get it, it will returned undefined. However, a key could exist with no value -- for example #key=val&novalue where novalue is a key with no value. If you do HashSearch.get("novalue") it would also return undefined. In which case, you should use HashSearch.keyExists("novalue") to verify that it is indeed a key.