I'm looking through the compatibility list for JS6 and its not promising. According to that list it will be at least 3 years before it is usable for everyday use. Is this correct?
Keep in mind that the page you linked doesn't take into consideration browser market share. For example, if there were a single browser with 100% coverage added to that page, the page as a whole would still look bad. However, if that browser accounted for 95% of all browser market share, things would actually be pretty good.
The page also doesn't consider importance of features, only if it's supported or not. While 100% compliance may be a long way off, vast amounts of useful features – like the spread operator – already have wide support.
In the meantime, as others have pointed out, there are many polyfill libraries available to help you bridge the gap until ECMAScript 6 is fully supported by all major browsers.
It is not JS6. It is ES6, or ES2015.
IE has ceased development and will always be red.
Although red, most non-syntax features can be shimmed, such as Array.from, Promise, and even WeakMap. Throw in a script and your code can use them.
In most browsers you can directly use arrow functions, new object syntax, template string, array spread, promise, for of, const/let etc.
They can simplify your code a lot.
Finally, we have Babel, which transforms your ES6 script to ES5 script. You can code ES6 now, run Babel, and get code that runs on any browsers. There are many ways to run Babel, from command line to in-browser.
Babel is the secret of the javascript chatroom people.
We are using ES6 now and using it daily.
A few language features simply cannot be done in ES5, in particular Proxy and subclassing, thus Babel do not support them. Firefox is the only browser to support Proxy, and Node.js supports an old syntax which can be shimmed into the final syntax.
As you can guess, they can do things totally impossible before, and may change how you design your program; such a radical change does take years to mature and spread, regardless of language.
Related
How to check the ECMAScript standard version that the currently installed JS on the system is using, is there any special command to know or we need to check the JS version and then Google it to know on which ES standard version it is based up on.
Environments do not run "a particular version of the standard." Rather, environments implement features from different years of the specification piecemeal. For example, it may be that in June 2022, a particular browser has implemented, say, 7 of 9 specification additions or tweaks from the prior year - and a different browser will implement those things on a different schedule.
Even if something is in the standard, there's no absolute guarantee that environments will support it, unfortunately. Usually they will, and often in a reasonably timely manner, but not always. For example, proper tail calls, from ES6, still have not been implemented in V8 or SpiderMonkey.
So, to figure out what is supported in a given environment, you'll have to test all the properties/features you're looking for individually. (eg window.hasOwnProperty('Promise'))
Often, rather than script-writers trying to detect what a browser currently supports, and working around that, script-writers will simply use a polyfill service (example) that adds all necessary missing features - that way you can get on with the main logic of your application and simply not worry about it.
Vanilla JS does not have any version as of Jquery,Angular, Reactjs, etc which are build using vanilla JS. It depends whether the current browser update supports upto which version of ECMA Script. You can use any version syntax as long as you can compile your code to ES5 syntax if your browser does not understand higher version of JS.
I implemented CKEditor on a project and I was surprised to discover, either in the interface or in the source code, that it's written in ECMA 6, using all its modern features such as the short function notation (arrow functions).
Given these features are not widely supported as the ECMA 5 version is (not yet as of today, July 2018), I ask why the developers made this strategic choice: are they not interested in a wide browser compatibility? Or is CKEditor so well spread to allow them to dictate a precise direction towards modern browser versions, risking to lose a portion of users?
Browsers are not a problem
Let's be clear here:
CKEditor 5 can be run in all browsers which it supports without any transpilation. All browsers which it supports have a sufficient level of ES6 support.
Why would you need ES5?
The only reason why you might want to transpile CKEditor 5 from ES6 to ES5 are:
Legacy browsers which it doesn't support (at least at the moment).
Existing setups which use ES6-incompatible JS minifiers (UglifyJS). It may be a bit inconvenient to include CKEditor 5 in such applications but, as it was commented already, we explain how to transpile CKEditor 5 to ES5.
Development environments for frameworks like React (create-react-app) or Angular (angular-cli) which didn't catch up yet and still require that libs kept in your node_modules/ are in ES5.
The last case is indeed a bigger problem because you don't have that much control over this environments as on your own projects. As I commented on Twitter:
3 years ago we decided that CKEditor 5 will be released in ES6 because all browsers which we planned to support should have a sufficient ES6 support by our ETA.
We were right – it worked great... in the browsers.
It turned out that the problem is in the build environments (create-react-app, angular-cli) which did not catch up.
We'll need to introduce ES5 builds just to satisfy these envs ;/
To clarify – I'm not criticising authors of these tools. It's more of an observation that we've been always worried about browser support while today the tools stop us.
And, as I mentioned in the other tweet, the problem is broad (e.g. finding a supported, stable, ES6+ compatible and fast minifier – see e.g. https://github.com/webpack-contrib/uglifyjs-webpack-plugin/issues/262 …).
Fortunately, the situation is improving:
#mtrebizan:
I think CRA 2.0 will be shipping non-transpiled code,just don't know how far release is. cc #dan_abramov
#dan_abramov:
There’s alphas you can try. Other than that the ETA is when the community makes it happen 🙂 there’s active work and you can help too
I know there was work in angular-cli on improving this situation too. So, in a relatively short time, all should work smoothly too.
Time aspect
The difference (in terms of features) between ES6 and ES5 is huge. Back in 2014, when we've been starting CKEditor 5 development, we chose ES5. ES6 wasn't standardised yet.
However, the situation changed in 2015. ES6 got published and our tests proved that all features we looked to (classes, generators, iterators, weak sets, weak maps, and more) were already available in Chrome. We decided to go for it and see.
About 1.5 year later CKEditor 5 worked natively (without any transpilation) in all modern browsers (with the exception of Safari which had a nasty bug). At the same time, babel-minify became usable so we didn't have to transpile CKEditor 5 to ES5 even for production.
It's 2018 and the number of obstacles was reduced even more. There's a chance that still this year you won't have to transpile CKEditor 5 to ES5 unless your project is supposed to be ES5 because of browser support (but then, why would you include CKEditor 5? it's not going to work in those browsers anyway).
Looking at the history of CKEditor 3-4, CKEditor 5 will stay with us for the next 8+ years. So, we're talking here about 2026+. This means that for the vast majority of its lifetime ES6 will not be a problem.
CKEditor supports vanilla javascript (ES5) and ES6 as well. The issue is not the editor, it just supports it, doesn't care about compatibility because it doesn't know where your code is going to run but only how to highlight and give you tools to develop it.
The thing is that, by the time, the ECMA standard is under heavy development, improving in every version, so there's a lot going on, there are a lot of proposals being added every month, some passes and makes their way into the standard, which later gets into cool features we can use like arrow function.
All of that makes it harder for browsers to catch on the new updates. Even so, there are a lot that supports the new features now (you may track the updates in that page).
Anyway, besides from all of that, you may use a code compiler like Babel (which compiles ES6/ES7... down to code the browsers can understand such as ES5). It's widely adopted, and recommended for the thing it does: Make your life easier. Many big companies adopted it, such as Facebook which uses react (and made it) using Babel to compile not only ES6 but JSX (check this).
Side note: Why should I use ES6 if I need a compiler?
https://itnext.io/why-you-should-use-es6-56bd12f7ae09
I want to use ES6 features in my script, and having all browsers support it. How can I do that, and can I?
I've been thinking about using some tool that will convert my code to ES5 automatically on git pulling it on the server, and create the second file out of it. And then in the browser I could use one of those scripts, depending on the browser and its version.
Is this possible?
It would however create some problems:
Converted code would have the same performance as writing the code
in ES5 natively.
I would have to write some kind of if in the HTML, and I want to
include just one script, without anything else.
What's the best way to do this?
Until more browsers support ES2015 (aka ES6) features, using transpilers and polyfills will be the only way to go. Checkout the ES6 compatibility table to determine what features you can use today for the browsers your site supports.
Keep in mind that there are two main parts to ES6:
new language features
new native API features
Until all the browsers your site supports have support for the new ES6 language features, you won't be able to use them in your scripts without first transpiling them to an ES5 equivalent. I've used babel and it has worked great. The ES5 equivalent code that is generated has performed just fine. It also beats me trying to write equivalent ES5 code manually. The code generated by babel has been thoroughly tested by babel's test suite and has been used by thousands of developers around the world. Also, writing your code with ES6 is shorter and easier to maintain. This saves a lot of developer time. When the day comes that when all the browsers your site supports have support for all the ES6 features, then you can turn off the transpiling step in your build and you'll get the full benefit of native browser performance without having to manually convert your manually written ES5 code to ES6.
Many of the new native API features can be used today by providing a polyfill. The polyfill is only needed when you want to use an ES6 feature AND you need to support older browsers. With a polyfill, only the older browsers may have slower performance compared to the native implementation. Since most of the modern browsers already support many of the native ES6 API features, many of your users will get the full performance of the browser's native implementation. From my experience with polyfills, I have not noticed any significant performance implications.
If you are concerned about modern browsers unnecessarily downloading and running the polyfill all for naught, then there are techniques you can to do minimize the impact:
On the server-side, you can detect the browser making the request and determine whether to bother sending the polyfill script tag in the response.
You can properly version the polyfill and make sure the web server's caching is set so the browser will rarely make a request for the polyfill after the initial download.
babel used to be able to transpile the ES6 code in your html files, but that feature has been removed. You can just move your embedded code to a separate external JavaScript file. If you don't like the idea of incurring another request to get this external JavaScript file, then you can do the following:
Write your ES6 code in a separate file.
Run this file through babel
Use your server-side scripting language to include the transpiled content directly in your HTML.
#DannyHurlburt's answer was correct at the time of posting it, but now, you can use TypeScript language (with .ts file extension) to work around this. TypeScript is a strict superset of JavaScript, so any ES6 code you have is also lexically valid TypeScript. TS compiles to old versions of JavaScript as old as ES3.
I am curious to understand/figure-out if the ECMAScript-6 new-changes will work on the old browsers or not.
Why I am asking this question is:
I remember the introduction of 'use strict'; in ECMAScript-5, it was meant for the compatibility with the old versions.
That means the old browsers will keep working fine and they will just ignore it when they encounter the 'use strict'; statement while parsing the new JavaScript code.
And the new JS-engines will treat the statement 'use strict'; in some special way as detailed here Strict mode.
So, coming to the question
I seriously doubt and curious to know how would the ECMAScript-5 compliant browsers behave when they will parse the ECMAScript-6 code.
The reason for my doubt is ECMAScript-6 new features involve syntax change/updates. And the old browsers which are new-syntax-unaware-engines will start throwing errors when they encounter any of the new syntax from the following
yield[*], Map, Set, WeakMap, function* foo(){}, =>, for...of etc.
My concern is has the decision/inclusion of new features in ECMAScript-6 taken care of supporting the old-browsers without any break of code?
If Yes then how?
If Not then what should I do to keep my old-browser-users happy?
I see one solution to keep the users using old browsers happy by including some transpiler like traceur-compiler in my project. This will convert my ECMAScript-6 code to ECMAScript-5 equivalent. But do I have any other solution to keep my old-browser-users happy?
What you are trying to explain here is forward compatibility. Obviously ES 5 ( or more precisely ES 5 engine ) is not forward compatible. Any way its hard to acheive and rare to find.
Although you can see that some of the features of upcoming ES 7 are already out and hence possibly ES 6's engine may be implemented considering those enhancement. So whenever ES 7 comes, some of the features will be working in older engine.
Answer to the question, is ES 6 backward compatible will be "yes". Yes! ES 6's engine will be happy to run ES 5's code but vice versa is not true.
Many ES6 features will not work in an ES5 JS engine, particularly new syntax features such as for/of or arrow functions, generators, etc.... Some features like the Set object can be partially polyfilled for older browsers, others cannot.
Of the list of features you had in your question:
yield[*], Map, Set, WeakMap, function* foo(){}, =>, for...of
None of those are compatible with older versions of Javascript and will either cause syntax or reference errors. Some characteristics of Map and Set can be polyfilled (though not all). Yield, generators, arrow functions and for...of are just new syntax that older browsers do not process and cannot execute. It is possible to use an ES6 transpiler that will convert your code to ES5-compatible code. That isn't really ES6 backwards compatibility, but rather a code conversion that uses only ES5 syntax to accomplish the same things that are expressed in the newer ES6 syntax. Some of that is done with polyfills and some done with alternative ways of expressing an ES6 construct using only ES5 code (and usually more ES5 code).
If your code runs in something like node.js or if it's a plug-in for a specific version of a specific browser, then you have better control over the JS engine and can likely use ES6 features sooner than in a browser.
If your code runs in a browser and you're not using a transpiler to conver to ES5 code, then it will be awhile (many years) until most browsers in use on the internet are all ES6 ready.
The different purpose of "use strict"; (removing support for bad practices) is more consistent with allowing for compatibility with older versions than new language features like generators as the "use strict"; construct was specifically chosen to be something that a new browser could detect, but an older browser would just see as a normal string. New ES6 features that represent new language syntax are simply not that way as older browsers don't know how to process them and even if they could somehow ignore the newer syntax, they don't support the functionality that the new syntax implies.
You may find this article useful which discusses some of the issues in trying to use ES6 today:
ECMAScript 6 Resources For The Curious JavaScripter
If you want to use most of ES6 capabilities today in a wide range of browsers, then your best option is probably to transpile your code using something like BabelJS. This will transpile your ES6 code into ES5 compatible code that will run in any ES5 browser. You get to write in ES6, but the code will run in a wide range of browsers.
Or, if you're running in only a specific environment (such as a browser plug-in for a specific version of that browser) or a specific runtime engine such as node.js, then you can write code that uses the ES6 features that are already supported in that specific engine.
In Coders at work, Douglas Crockford discusses how bugs in browsers cause Javascript to be a complex, clunky language and fixing it is a catch-22. In Beginning JavaScript with DOM scripting and Ajax Christian Heilmann says something similar "[The] large variety of user agents, of different technical finesse [...] is a great danger to JavaScript."
Why doesn't JS have a breaking new version? Is there something inherent n the language design where backwards compatibility becomes a must?
Update
Why can't javascript run with multiple engines in parallel? Similar to how .NET runs versions 2, 3 and 4 on the same machine.
Lazy copypasta at OP's request:
JavaScript is just a programming language: syntax and semantics. It has no built-in support for browsers (read: the browser DOM). You could create a JS program that runs outside of a browser. You (should) know what an API is - the DOM is just a JavaScript API for manipulating an HTML page. There are other DOM APIs in other languages (C#, Java, etc.), though they are used more for things like XML. Does that make sense?
Perhaps this MDC article can clarify further.
Well a breaking change would break a lot of existing websites, which would make a lot of people very angry :)
Backwards compatibility is important because of the large number of browsers deployed and the wide variety of versions of those browsers.
If you serve a new, incompatible kind of Javascript to old browsers, they all break.
If you invent a new language that is not considered to be Javascript by existing browsers, then it doesn't work with the majority of browsers. Very few users will be willing to download a new browser just to work with your new language. So web developers have to keep writing compatible Javascript to support the majority of the users, no matter how great the new language is.
A lot of people would like to see something better than current Javascript be supported by browsers, but it just isn't going to happen any time soon. All the makers of browsers and development tools would have to support the new thing, and continue to support the old Javascript stuff too. Many interested parties just wouldn't consider the benefit to be worth the cost. Slow evolution of Javascript seems to be the only viable solution.
As a matter of fact, ECMAScript 5 is not fully backwards-compatible for the very reasons you mentioned.
Inertia.
Making a breaking change would break too many sites, no browser vendor would want to deal with all the bug reports.
And PHBs would be against targeting a new version, why should they have their developers write javascript for the broken and the fixed languages? Their developers will have to write it for the broken version anyway so why bother with 2 implementations (which from a developer perspective sucks too since now they have to update, support and debug 2 separate trees).
Ecmascript 5 has a "strict" mode. I think this strict mode is intended to combat the problem you mention. Eventually you'd mark scripts "strict" that you want to use the new engine, all others get run in an old crufty VM, or with un-optimized codepaths or whatever.
This is kind like IE and Mozilla browsers having multiple "modes" of rendering websites (IE even swaps out rendering engines).
See this question about it
Javascript has subtle differences across different browsers. This is because each browser manufacturer has different sets of responsibilities to their users to support backwards compatibility (if any). If I had to pick, I'd say the biggest barrier to the advancement of javascript is older versions of Internet Explorer. Due to service agreements with their users, Microsoft is contractually obliged to support older browsers. Even if other browsers cutoff backwards-compatibility, Microsoft will not. To be fair, Microsoft does realize how terrible their browsers are and will hopefully push IE 9.0 very hard. Despite the inconsistencies of javascript across different browsers, they are subtle enough to make cross-browser programming more than feasible. Abruptly cutting off backwards-compatibility would be a practice that would make web development a nightmare. Incrementally cutting of backwards-compatibility for specific aspects of javascript is feasible.
There is much more else wrong with JavaScript. You can't be fully backwards-compatible with things that were never fully compatible when they were fresh... Say, the length of the array [1,] is reported as 2 by at least older versions of internet explorer.
The biggest fault of JavaScript is that is comes with a tiny, incomplete and pretty much unusable standard library. That is why everyone retreats to using jQuery, Dojo, Mochikit etc. - these offer mostly functionality that should be part of some standard library included with the browsers instead of floating around in thousands of copies and versions. It's actually what makes .NET and Java so popular: the language comes with a reasonable standard library. With C and C++, you have to dig out the nice libraries (Boost e.g.) yourself.
But other than that, the ECMAScript standard occasionally is updated.
Google is also trying to do this bold step forwards and redo JavaScript in a slightly more sane way. The efforts are known as Dart: http://www.dartlang.org/
For all I can tell, Dart largely uses the syntax of JavaScript minus a couple of its quirks. Apart from that, it also is nicer for the virtual machine and will thus likely run faster (unless of course you compile Dart to Javascript and use a JavaScript VM; which is offered as a compatibility option). But of course any hardcore JavaScript nazi^W enthusiast will not like anything that claims to be better than JavaScript. Whereas for me, they don't go far enough. In particular, they still don't provide enough "classpath".