At this level, the browser doesn’t know or care about Ajax requests. The HTTP and Cache sub-systems of modern browsers are at a much lower level than Ajax’s XMLHttpRequest object. Fact #1 : Ajax Caching Is The Same As HTTP Caching The rest of this blog post covers two important facts that will help you understand and effectively apply caching to Ajax requests. Make sure your Ajax requests follow the performance guidelines, especially having a far future Expires header. Rule 14 of High Performance Web Sites states: However, due to their dynamic nature people often overlook the benefit of caching them. To use this indexing scheme you would first need to change all your fragment identifiers to start with a ! symbol:Īugin Caching, Firefox, HTTP, HttpWatch, Internet ExplorerĪjax calls are just like any other HTTP request that might be used to build a web page. To overcome this problem Google supports a convention that allows the Googlebot to turn fragment identifiers into query string parameters. This means it would be impossible for Ajax driven sites to be indexed and have their fragment URLs returned directly in Google searches. Any JavaScript used by your page to load or build content will not be executed. As a consequence, it will normally ignore fragment identifiers and just look at the resource returned from the web server. It fetches and parses HTML, but it’s not a full blown browser and doesn’t have a JavaScript engine. The Googlebot is responsible for crawling sites to find content and embedded links that will become part of the Google search index. The fragment identifier specifies the embedded help topic page:Ħ. The solution was to use fragment identifiers and JavaScript to create linkable URLs. Although the content was easily accessible in the browser, the URL in the location bar didn’t change as you moved between topics making it practically impossible to share URLs for topics of interest. We recently deployed the help and automation reference for HttpWatch on our web site using the frame based HTML generated by the help authoring tool. As described in 4) this can be used to add history entries for a page without forcing a complete reload. The window object’s hash property allows JavaScript to manipulate the current page’s fragment identifier. JavaScript Can Use to Change Fragment IDs These features are particularly useful when used with JavaScript (see below) to create linkable URLs and history for pages that either use top level HTML frames or update their content dynamically with Ajax calls. However, it does add an entry in the browser’s history so that clicking the Back button will go back to the original location in the page. Rather, it will continue on its way, output “Hello!” to the console, and then when the request returns a couple of hundred milliseconds later, it will output the number of repos.And the browser scrolls the page to the new location but doesn’t reload the page. It will not, however, wait for the request to complete. The JavaScript interpreter will encounter the fetch command and dispatch the request. This is because fetching data from an API is an asynchronous operation in JavaScript. If you run this code, it will output “Hello!” to the screen, then the number of public repos attributed to my GitHub account. Execution goes from top to bottom.Ĭontrast that with the equivalent JavaScript version: fetch ( '' ). It then parses the response, outputs the number of public repos attributed to my GitHub account and finally prints “Hello!” to the screen. It’s a neat and effective way to introduce a delay without breaking a sweat.Īs one might expect, this code makes a request to the GitHub API to fetch my user data. Then, after a brief two-second pause, “World!” will follow. Run this code, and you’ll see “Hello” pop up in your console. Here’s the most straightforward way to add a sleep function to your JavaScript toolbox: function sleep ( ms ) ) How to Create a Sleep Function in JavaScriptįor those of you who are here for a quick fix and don’t want to dive into the technical details, we’ve got you covered. Best Practices for Creating a JavaScript Sleep Function.How to Write Better Sleep Function in JavaScrip.Increasing Timeouts as Alternative to Sleep Function in JavaScript. setTimeout() Function Examining and Best Practices.How to Use SetTimeout in JavaScript Properly.Understanding JavaScript’s Execution Model.How to Create a Sleep Function in JavaScript.
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