ajax and html5 change page URL without refresh

Performance

If you use chrome or firefox and other browsers to visit this blog, github.com, plus.google.com and other websites, if you are careful, you will find that the clicks between pages are requested asynchronously through ajax, and at the same time the page The URL has changed. And it can support browser forward and backward very well.

What is it that has such a powerful function?

HTML5 references new APIs, history.pushState and history.replaceState, which are used to change the page URL without refreshing.

Differences from traditional AJAX

Traditional ajax has the following problems:

1. The page content can be changed without refreshing, but the page URL cannot be changed

2. For better accessibility, after the content is changed , usually change the hash of the URL

3. The hash method cannot handle the browser's forward and backward problems well

4. Furthermore, the browser introduces the onhashchange interface, and browsers that do not support it can only judge the hash regularly. Will it be changed

5. But this method is very unfriendly to search engines

6. Twitter and Google have agreed to use #!xxx (that is, the first character of hash is!), and search engines support it.

In order to solve the problems caused by traditional ajax, new APIs have been introduced in HTML5, namely: history.pushState, history.replaceState

You can operate the browser history and change the URL of the current page through the pushState and replaceState interfaces.

pushState is to add the specified URL to the browser history, and replaceState is to replace the current URL with the specified URL.

How to use

var state = {
    title: title,
    url: options.url,
    otherkey: othervalue
};
window.history.pushState(state, document.title, url);

In addition to the title and url of the state object, you can also add other data, for example: you also want to save some configurations for sending ajax.

replaceState and pushState are similar, so I won’t introduce them here.

How to respond to the browser's forward and backward operations

The onpopstate event is provided on the window object. The state object passed above will become a sub-object of the event, so that the stored title and URL can be obtained.

window.addEventListener('popstate', function(e){
    if (history.state){
        var state = e.state;
        //do something(state.url, state.title);
    }
}, false);

This way, you can combine ajax and pushState for perfect refresh-free browsing.

Some restrictions

1. The passed URL must be in the same domain and cannot cross domains

2. Although the state object can store many custom attributes, it cannot store non-serializable objects, such as: DOM object.

Corresponds to some processing on the backend

In this mode, in addition to using ajax to browse without refreshing, it is also necessary to ensure that the changed URL can be browsed normally after directly requesting it, so the backend needs to process these.

1. Send a special header to ajax using pushState, such as: setRequestHeader(‘PJAX’, ‘true’).

2. When the backend obtains the header with PJAX=true, the common parts of the page will not be output. For example: PHP can make the following judgment

function is_pjax(){
    return array_key_exists('HTTP_X_PJAX', $_SERVER) && $_SERVER['HTTP_X_PJAX'] === 'true';
}

Although there are only pushState, replaceState, and onpopstate on the interface, a lot of processing is required when using it.

A plug-in based on jquery has been written for this, and ajax+history.pushState has been encapsulated into pjax. Project address: https://github.com/welefen/pjax. Currently, 3 versions of jquery, qwrap, and kissy are supported.

In addition, if you want to consider the effect of both HTML4 and HTML5, you can refer to history.js. The project address is: https://github.com/browserstate/history.js.

Reference materials:

1. Introducing the HTML5 History API

2. Manipulating the browser history

3. Session history and navigation