HTML5 History API provides a way to maintain history of the current session. This information can be used for page navigation. It really comes in handy when we are using AJAX to load pages and want to have browser navigation (back/forward) active. Using HTML5 History API, we can maintain the history and use it for navigating back and forth using browser's navigation button.
We will use hashchange event and hashtags for urls. To navigate using the browser's default navigation buttons, i.e, by using the back and forward buttons, there must be a change in the URL. The navigation buttons get active only if the URL of the current window (page) changes. When we use AJAX (JSON), the URL of the current window doesn't change. So we won't have any active navigation, which implies, no history as well.
To add hash to the URL without causing the page navigation, we'll use window.history.pushState(null, "", "#hashtag") method. We need to be concerned mainly about the third parameter, which is the hashtag string. After that we'll trigger a hashchange event $(this).trigger("hashchange");.
These are some of the notable functions in the history API.
window.history.pushState(data, title, url)
@param data
data is generally something that is specific to the context of the particular page. Say in the first page you retrieve data in JSON format. Say our data is:
{
"page": "1",
"title": "Tutorial",
"category": "HTML5",
"desc": "intro"
}So when we want to navigate to another page we can save that data so that, the next time when we revisit, popstate will fire and you can retrieve the data through event.originalEvent.state object.
@param title
The second parameter can be any string.
@param url
Can be hashtag or a string. Note that you can't change the baseURI, or it will throw SECURITY_ERR exception. Otherwise it will be easy for URL spoofing. This value will be appended to the baseURI without loading the appended URL. This will activate the browser history, so that we'll have active back and forward button.
The 'popstate' event
When you navigate in history, popstate will be fired, and the data corresponding to the state will be popped. Theses data objects are kept in a stack using the pushState function explained above.
window.location.hash
This variable will contain the current hashtag of the window
The 'hashchange' event
hashchange event is will be fired whenever there is a change in navigation, i.e if you travel back and forth in history, each time the hashchange event will be fired. So we can listen for the hashchange event and depending on the hash, which we can obtain from window.location.hash, we can take the necessary action. Since we already listen for the hashchange event, we'll trigger the event when the user clicks the page's anchor link to go to that particular page. Otherwise, we can write a separate way to deal with clicking anchor links as opposed to clicking back/forward buttons, which isn't really necessary. So that's the reason we trigger hashchange event manually.
window.history.replaceState(data, title, url)
This function is same as that of push state. But instead of pushing a new state to the stack, it will replace the top state (from the stack) with the one specified in this function.