Windows 10: Microsoft Edge and Fetch (or the undeniable limitations of XHR)

Brink · May 23, 2016

Starting in EdgeHTML 14, coming with this summer’s Windows 10 Anniversary Update, Microsoft Edge will support the highly anticipated Fetch APIs. This represents the first step in our planned journey to supporting Service Worker in a future release. You can preview the Fetch APIs in Windows Insider Preview builds starting with EdgeHTML 14.14342.

XHR: the beginning

The journey to Fetch started with XMLHttpRequest (XHR), first pioneered in IE5 (as part of the MSXML ActiveX control) and now one of the foundational components of modern web functionality. Most sites today use XHR, often via a helper method that abstracts away its unpleasantness (such as the $.ajax() method in jQuery), rather than directly (for example, via the open method, setRequestHeader method, send method, and onreadystatechange event listener). One of the many reasons to use a JavaScript library such as jQuery is to make it easier to interface with XHR, especially when these libraries take advantage of new JavaScript concepts such as Promises.

Along came Fetch

Unfortunately, libraries aren’t well-equipped to interact with the low-level constructs of requests and responses, because the XHR APIs do not expose those concepts. More importantly, there hasn’t previously been a way to get at any resource request that occurs in the browser, for instance, the CSS files and image files included as part of the HTML of a page. Developers were only able to operate on requests and responses when making explicit XHR calls in JavaScript. This posed an interesting challenge for newer features, such as Service Worker, which needed to intercept any fetch that occurs in the browser, as well as features that relied on a standardized process by which resources can be retrieved, such as sendBeacon.

Because of this, the web needed a new spec to unify the concepts of fetching resources, CORS, and redirect handling across the web platform. There was also a need to introduce new APIs that would give access to the primitives that would allow interfacing with the requests and responses.

Why not extend XHR?

The XHR2 spec prioritizes backwards compatibility with the first iteration of XHR; this resulted in XHR2 being restricted to XHR’s dated object model. Building a brand new API from the ground up means it can be unshackled from the old API’s model. XHR could have been extended to have the same capabilities of the Fetch API, but it would have been an ad-hoc addition that would have made little sense in the context of any and all resource requests from the browser. Starting over and introducing the lower-level primitives that represent the requests and responses allowed for a far more extensible and robust API that also leverages new platform primitives such as Promises.

To fetch or not to fetch?

All of this raises the question of why developers should use the new Fetch APIs if they can already accomplish the same tasks with XHR. Let’s walk through a few of the several reasons for using the Fetch APIs: modern APIs, streaming, and future-proofing...
Click to expand...

Read more: Fetch (or the undeniable limitations of XHR) | Microsoft Edge Dev Blog

:)

Janeane Cru · May 23, 2016

limitation on microsoft Edge and microsoft Photos

Hi Richard,

This Windows 10 question is more complex than what is typically answered in the Microsoft Answers forums. It is better suited for the IT Pro audience on TechNet. Please post your question in the TechNet
Windows 10 Networking forum.

Let us know if you need further assistance.

Dan LeBlanc · May 23, 2016

limitation on microsoft Edge and microsoft Photos

I have this exact same issue. Did you ever find a fix for this?

Windows 10: Microsoft Edge and Fetch (or the undeniable limitations of XHR)

Microsoft Edge and Fetch (or the undeniable limitations of XHR)

Microsoft Edge and Fetch (or the undeniable limitations of XHR)

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