To visit another page on the website, the visitor goes to a different URL that points to a different.(The page might also load other files like JavaScript and CSS, but it’s all referenced by the HTML file.) html file contains all of the content on the page, and it’s loaded all at once. A visitor goes to a URL that points to a particular.(Try refreshing this example to see different welcome messages.) Thinking in AJAXīefore AJAX, most websites worked like this: See the Pen by Happy Coding ( on CodePen.
Javascript fetch code#
In other words, this code displays a random welcome message (which are specified in a separate. Then the code picks a random message, and uses it to set the content and color of the page. This code fetches the JSON from the file and then parses that JSON into an array using the json() function.
Behind the scenes, asynchronous functions return a Promise object, which is a special value that lets you specify what happens when the work is done. You can think of an asynchronous function as promising to do something when you call it. This is handy for actions that might take a long time to complete, like fetching the content at a URL. So far, the functions you’ve seen have been synchronous, which means they happen right away, as soon as you call them.įunctions can also be asynchronous, which means they happen “behind the scenes” while the rest of your code keeps running. You can also use your own files, but you have to either run a local server or upload them to a web host like GitHub Pages. To make your life a little easier, you can use these files for now: Imagine how scary the internet would be if any website could read files from your computer!īut this might also make it more annoying to test out your code as you read through this tutorial. The fetch() function lets you load other files on the internet, but it does not work with local files loaded using file:// URLs. This function lets you load another URL and then add its content to your webpage, or do other processing with it. That sounds complicated, but with modern JavaScript, using AJAX means calling the fetch() function. AJAXĪJAX stands for Asynchronous JavaScript and XML. This tutorial introduces another approach called AJAX, which you can implement using the fetch() function. There are a few ways to do that: you could write JavaScript that manipulates the page, or you could use something like Jekyll or a server to build the HTML. Then when you want to change the message, you could change it in one place instead of changing it in each individual file. It would be nice if you could put your message in a single place that every. That might be okay for three files, but what if you have a dozen pages? Or a hundred? What happens when you want to change the message to something else? You could do this manually by editing each.
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