dojo/hash — The Dojo Toolkit

since:	1.4

Introduction ¶

dojo/hash is designed to make it easier to manage the browser history (hash) as well a provide cross-browser ways to support dynamic backwards and forwards navigation and bookmarkability. This allows for creating of dynamic web applications that can be navigable both in a non-linear fashion, but allows for you to provide your users with a “URL” to be able to return to a particular point in the application without actually doing a full page reload.

HTML5 defines an onhashchange event that fires when the value of the hash segment of the URL changes. See HTML5 History. dojo/hash uses the native onhashchange event if the browser supports it, and emulates this support for older browsers using a polling loop.

Usage ¶

Running code when the browser hash changes works by loading the dojo/hash module and then subscribing to the appropriate topic:

require(["dojo/hash", "dojo/topic"], function(hash, topic){
  topic.subscribe("/dojo/hashchange", function(changedHash){
    // Handle the hash change publish
  });
});

The value of the change of the hash will be passed as the first argument.

To manipulate the value of the hash, simply call dojo/hash with the new value. It will be added to the browser history stack and it will publish a /dojo/hashchange topic, triggering anything subscribed:

require(["dojo/hash"], function(hash){
  hash("someURL");
});

In order to not to add to the history stack, pass true as the second parameter (replace). This will update the current browser URL and replace the current history state:

require(["dojo/hash"], function(hash){
  hash("someURL", true);
});

To get the current value of the hash, simply call the function without any arguments:

require(["dojo/hash"], function(hash){
  var currentHash = hash();
});

Examples ¶

Subscribe to the hashchange event:
```
require(["dojo/topic", "dojo/hash"], function(topic, hash){
    topic.subscribe("/dojo/hashchange", context, callback);
});
```
require(["dojo/topic", "dojo/hash"], function(topic, hash){ topic.subscribe("/dojo/hashchange", context, callback); });

Set the hash using query notation:

require(["dojo/hash", "dojo/io-query"], function(hash, ioQuery){
    var obj = {
        firstParam: true,
        secondParam: false
    }
    hash(ioQuery.objectToQuery(obj));
});

Hash: #firstParam=true&secondParam=false

Parse this hash and add a parameter using query notation:

Initial hash: #firstParam=true&secondParam=false
require(["dojo/hash", "dojo/io-query"], function(hash, ioQuery){
    function updateHash(){
        var obj = ioQuery.queryToObject(hash());  // get
        obj.someNewParam = true;
        hash(ioQuery.objectToQuery(obj));  // set
    }
});
require(["dojo/hash", "dojo/io-query"], function(hash, ioQuery){ function updateHash(){ var obj = ioQuery.queryToObject(hash()); // get obj.someNewParam = true; hash(ioQuery.objectToQuery(obj)); // set } });
End hash: #firstParam=true&secondParam=false&someNewParam=true

React to hashchange event (hash passed to callback as first param):

require(["dojo/hash", "dojo/io-query"], function(hash, ioQuery){
    function callback(hash){
        // hashchange event!
        var obj = ioQuery.queryToObject(hash);
        if(obj.firstParam){
            // do something
        }
    }
});

Get and set the hash using slash notation:

Initial hash: #/firstSegment/secondSegment
require(["dojo/hash"], function(hash){
    function updateHash(){
        var obj = hash().split("/");
        obj.push("trailingSegment");
        hash(obj.join("/"));
    }
});
require(["dojo/hash"], function(hash){ function updateHash(){ var obj = hash().split("/"); obj.push("trailingSegment"); hash(obj.join("/")); } });
End hash: #/firstSegment/secondSegment/trailingSegment

Notes ¶

Customizing the Polling Loop Frequency ¶

For browsers that do not support the onhashchange event natively, a polling loops monitors the URL for changes. The default duration of this polling loop is 100 ms. To customize this value, add hashPollFrequency to dojo config.

dojoConfig = { hashPollFrequency: 200 };

Encoding/Decoding ¶

dojo/hash does not attempt to do any encoding or decoding. There are many cases where consumers of dojo/hash want unencoded slashes, etc, so it is up to the consumer to encode and decode where appropriate. Anything with HTML encoding (e.g. &) must be encoded with encodeURIComponent before being passed into dojo/hash due to discrepancies between browsers. For example Firefox decodes HTML encoding automatically before setting the URL, IE does not.

require(["dojo/hash"], function(hash){
  hash(encodeURIComponent("hash with & HTML encoding"));
});

dojo/hash ¶