Although the Chrome browser has been in its inception for six years, it is rapidly entering its maturity in version numbers. Chrome 39 is now available, and you may have installed it. This release contains some nice new features…and a slightly suspicious addition or two.

ECMAScript 6 Generator

The

Generator is a special function declared using function* to create an iterator. An iterator is an object with a next() method that is called to return a value. The generator function uses the yield statement to provide the next value in the sequence.

Arunoda Susiripala provides a basic example in JavaScript Generator and Callback Prevention:

function* HelloGen() {
    yield 100;
    yield 400;
}

var gen = HelloGen();

console.log(gen.next()); // {value: 100, done: false}
console.log(gen.next()); // {value: 400, done: false}
console.log(gen.next()); // {value: undefined, done: true}

Chrome, Opera, and Firefox 31 support ECMAScript 6 generators.

Beacon API

The new Beacon API allows you to send data to the server without waiting for a response. Requests will be queued and the browser will send these requests as soon as possible, but it is important that it will not delay the uninstallation of the current page or the loading of the next page.

navigator.sendBeacon() will receive a URL and data (probably a string or a FormData value). Usually, it can be used to transfer statistics, for example:

navigator.sendBeacon('/log', 'page-unloaded');

If the browser successfully queues up a Beacon request, the method returns true. I'm not sure what can be done if false is returned, but Beacon doesn't apply to basic functionality or messaging.

Chrome, Opera, and Firefox 31 support the Beacon API.

Web animation control

Web animations are available in Chrome 36. The concept is to allow simple CSS3-like keyframes and animation declarations from JavaScript, such as:

var myanimation = myelement.animate([
    { color: "#f00" },
    { left: "20em" },
    { transform: "rotate(180deg)" }
], {
    duration: 1000,
    iterations: 1,
    delay: 0
});

The advantage is that you can control and synchronize playback based on user input or other conditions. Chrome 39 adds playback methods such as play(), pause(), reverse(), finish() (put the animation to its final state) and cancel() (clear all effects).

A tradeoff between thinking of web animation as simple CSS3 animation and complex JavaScript full-frame control using requestAnimationFrame and your own timing functions. It may be a bit too much for the average web effect, but it is not powerful enough for the game. Apps and presentations might be good use cases?

Currently, only Chrome and Opera browsers support web animations. Support is available in Firefox nightly versions and polyfill is available, but the technology will not be stable for a while.

Web application list

Don't be confused with the application cache manifest, a web application manifest is a JSON file where you can place metadata such as name, start address, icon, display mode, orientation, etc.

You need to add a link to the HTML header:

<link rel="manifest" href="manifest.json">

and the manifest file itself, for example:

function* HelloGen() {
    yield 100;
    yield 400;
}

var gen = HelloGen();

console.log(gen.next()); // {value: 100, done: false}
console.log(gen.next()); // {value: 400, done: false}
console.log(gen.next()); // {value: undefined, done: true}

This ultimately means we can remove 57 alternatives to iOS icon sizes from the top of each page...Suppose Apple decides to implement this technology in Safari!

Cross-browser support is uneven. Firefox uses the list for its market, but there seems to be some differences in the property name.

Windows 7 Immersive Mode

Switching to immersive mode on Windows 7 will make Chrome behave a bit like a Windows 8 full-screen Metro app. Strangely, it places a translucent taskbar similar to Chrome OS above the Windows taskbar—with its own start button and clock.

Why? If Windows 7 users want a Windows 8 experience, they can upgrade. However, there is a reason many Windows 7 users choose to stick with the operating system: they don't want Windows 8!

I'm also confused by Google's insistence on sneaking up on Chrome OS widgets to other operating systems. The Chrome app icons here and there are OK - but copying native features makes no sense. Maybe they want to attract people to use Chrome OS, but annoying them won't help.

Other updates

There are also some smaller features...

• You can now install the free Chrome app in the Play Store without logging in.
• On the high DPI/Retina screen, scrollTop and scrollLeft now return the score of the pixel. If you think pixel perfection is bad, wait for the customer to start asking for subpixel perfection!
• You can now edit the saved password.
• Now, only 64-bit versions of Chrome are available on Mac OS.
• SHA-1 encryption is being phased out, replaced by SHA-2.
• Experimental support for the extension button icon in the menu has been added (set Enable extension toolbar redesign in about:flags).

While some of the added problems and Firefox caught up with some features, the 39 version is still a great update. Chrome is still fast and stable, and is the preferred browser for nearly half of the web users. Recommended use.

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