Which version of JavaScript does Google Chrome support in relation to Mozilla Firefox? In other words, does Chrome support JavaScript 1.6, 1.7, or 1.8 which Firefox also supports or some combination of them?
While Chrome will execute Javascript marked as "javascript1.7", it does not support JS1.7 features like the "let" scoped variable operator.
This code will run on Firefox 3.5 but not on Chrome using V8:
<script language="javascript" type="application/javascript;version=1.7">
function foo(){ let a = 4; alert(a); }; foo();
</script>
If you change language to "javascript1.7" and omit the type, it won't run with JS 1.7 features in Firefox 3.5. The type section is necessary.
This seems to be related to a general WebKit bug, https://bugs.webkit.org/show_bug.cgi?id=23097; it may be that Chrome emulates the Safari behavior even though it uses a different engine.
When asked about supporting JS 1.8 features, the V8 team said they were trying to track the version used in Safari so pages would act the same in both browsers.
This thread is still relevant. As of 2012, Chrome supports most of Javascript 1.6, not including string and array generics. It supports none of 1.7. It supports reduce and reduceRight from 1.8, all of 1.8.1, and Getters and setters and all the non-version specific things listed on this page. This page is linked from the Mozilla Developer Network, which specifies the versions of javascript, found here.
Google Chrome uses the V8 javascript engine, which currently states that it implements ECMA-262, 3rd edition. This would imply it supports at least version 1.5.
Here's a simple Javascript 1.6 feature Chrome (and V8 users, like node.js) won't run: for each … in
for each (variable in object)
statement
As it is JS 1.5 (per J c's answer) is the only version Chrome claims to completely implement.
In fact the Chrome team has mostly aimed for compatibility with Safari (most prominent Webkit user at the time), and refused features on those grounds.
Google Chrome supports up to Javascript 1.7:
<script language="javascript1.7">alert(1.7);</script> - Alerts
<script language="javascript1.8">alert(1.8);</script> - Doesn't alert
This is an old thread, however here goes. Google Chrome does not respond to the following
function foo(){
let a = 4;
alert(a);
}
foo();
hence it does not support JavaScript 1.7
Related
We are starting a project and want to be cross-browser compatible - this would seem to suggest that we need to ensure that the version of JavaScript we're using is works in all of the browsers we intend to support. Is the following a reasonable way to test to see what the JavaScript level works in each browser?
<script language="javascript1.0">alert("Your browser at least supports JavaScript 1.0");</script>
<script language="javascript1.1">alert("Your browser at least supports JavaScript 1.1");</script>
<script language="javascript1.2">alert("Your browser at least supports JavaScript 1.2");</script>
<script language="javascript1.3">alert("Your browser at least supports JavaScript 1.3");</script>
<script language="javascript1.4">alert("Your browser at least supports JavaScript 1.4");</script>
<script language="javascript1.5">alert("Your browser at least supports JavaScript 1.5");</script>
<script language="javascript1.6">alert("Your browser at least supports JavaScript 1.6");</script>
<script language="javascript1.7">alert("Your browser at least supports JavaScript 1.7");</script>
<script language="javascript1.8">alert("Your browser at least supports JavaScript 1.8");</script>
Obviously the list of tests could be extended as further JavaScript versions are released.
Is there a better way (or source) for this information?
By the way, I did see the Wikipedia page on JavaScript versions and it doesn't seem to correspond to the results I get when I run the code snippet above.
My results are:
Firefox 43.0.4 - reports as supporting JavaScript 1.0 through 1.5
IE 10.0.9200.17566 - reports as supporting JavaScript 1.1 through 1.3
Chrome Version 47.0.2526.111 m - reports as supporting JavaScript 1.0 through 1.7
Safari 5.1.7 (7534.57.2) - reports as supporting JavaScript 1.0 through 1.7
Opera 34.0.2036.50 - reports as supporting JavaScript 1.0 through 1.7
Is the following a reasonable way to test to see what the JavaScript level works in each browser?
No.
Don't use the [language] attribute, it's only going to cause you incompatibility, especially as time goes on and newer browsers decide they only support javascript3.8 or whatever the version-du-jour happens to be. If you want to write a script, just write a script:
<script src="filename.js"></script>
As far as detecting versions, you don't need to detect JS versions. No developer worth their salt checks versions, they check features. Modernizr is one such feature detection resource. caniuse is another which describes which browsers support which features so you can determine if you're going to be able to use any particular feature at all.
In many cases, what you'll want for maximum backwards compatibility is a set of polyfills to replicate any newer features you'd like to use for older browsers.
I don't understand the best way to use "let" keyword...
In IE11 and Chrome45 I can use it fine
In Safari8.0.4, like in older versions of Chrome, it gives the error "unexpected use of reserved word 'let'"
In Firefox the let keyword only works inside <script type="application/javascript;version=1.7"/>, but this script type isn't even recognized as Javascript in IE11, Chrome45, Safari8.
Here's a JSFiddle that shows it in action: https://jsfiddle.net/p6cgtyg6/1/
So -- I don't mind requiring users to use modern versions of their browsers.
And I don't mind excluding Safari if there honestly is no version of Safari that supports this keyword. (Is that really true? Why does everyone spend all their time griping about IE when Safari seems so much worse in ES6 terms? Have I missed something?).
But how should I allow "let" to work in Firefox while not preventing Chrome/IE? (I haven't yet found links from people griping about how Firefox script tag behaves differently from Chrome, and I'd have expected more complaints, so I figure I must have missed something obvious...)
Concerning Safari 8, it's just not supported ; for that browser, I'd recommend using Babel.
If you have the gut feeling that this bug won't be fixed anytime soon* then you could have a script that detect Firefox which would then inject your script(s) with the appropriate value for the type attribute.
As a side note, I would advise not to use let blocks—unless you wanna use this transpiler—nor let expressions which will be dropped.
* fixed in Firefox 44
let is a part of ECMAScript 6 specification, and ECMAScript 6 itself is in 'draft' status. Even in its incomplete form its features aren't supported fully by actual browser versions.
Since you want to dive into ES6 today for production, your best bet is to use ES6 to ES5 transpiler, most prominent ones are Babel and Traceur, which are available as both CLI and packages for the build system of your choice. There are online tools for Babel and Traceur to try them out. And Scratch JS extension for Chrome uses both Babel and Traceur and is excellent for developing and compiling ES6 scripts if the build system is not an option.
Here is up-to-date comparison table that embraces ES6 feature support in both browsers and ES6 compilers.
And here is a great collection of ES6-related tools.
See browser compatability of this ES6 keyword.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let#Browser_compatibility
Also see this SO post for ES6 feature detection.
I can't seem to find any information, but i have Firefox version 24 and when i look at the version of javascript that it uses, i get version 1.5. This is giving me constant headaches because i should have the 1.6 version. I have many bugs and problems with my javascript code related to this problem.
Does anyone know why FF ships with version 1.5 and how can i get the 1.6? I allready lookt up the mozilla forums and developer network, but no help there.
All my other browsers, safari, chrome and opera have newer javascript versions.
See this fiddle:
JavaScript is the original name that Mozilla gave to the language (LiveScript really, but that's history now). All browsers implement ECMAScript, what we know today as JavaScript. JavaScript 1.x is the internal versioning of Mozilla's implementation of ECMAScript. You should be comparing supported features not different implementations of the language since they all implement the same standard, ECMA.
We have written a lot of horrible jscript code for server side classic ASP (the current platform of some very big blue chip companies which are our customers). jscript is more or less javascript version 1.3. It doesn't have built in JSON libs, and doesn't have some of the newer loop constructs for example
The question is, can the dart JavaScript compiler target older versions of JavaScript?
No. See Q. What browsers do you plan to support as JavaScript compilation targets?.
We're currently aiming to support the following browsers:
Internet Explorer, latest two versions that are 9 or higher.
Firefox, latest two versions that are 7 or higher.
Chrome, latest version.
Safari, latest two versions that are 5.1 or higher.
Opera, latest version that is 12 or higher.
That's a goal; we don't actually support all of these browsers yet. The goal may change to be either more restrictive or more permissive. We'll refine this further as Dart matures.
I think the main reason is to have a browser that contains a quite recent version of javascript.
For instance, you can find some calls to Object.create (requires JavaScript 1.8.5) in the js file resulting of dart2js compilation.
The Mozilla Foundation continues to add new language features to JavaScript. They're up to version 1.8 now where 1.5 was more or less the ECMA baseline.
However, Firefox is the only browser that supports the latest version and IE is firmly stuck at a 1.5-equivalent JScript.
What purpose do the Firefox-only extensions serve? Or are they just lying dormant until (and if) the rest of the browsers catch up?
Firefox, Thunderbird, and other XUL apps also have large portions of themselves written in JavaScript. A more featureful JavaScript means a better development environment for Firefox and other Mozilla apps.
Extending the language is a good idea, even if only one browser is doing it - eventually it will prove itself and be made into the standard at which time other browsers will have to catch up.
Otherwise, how can progress be made - Microsoft does this all the time: would XMLHttpRequest have ever made it into the standards if Internet Explorer wouldn't have implemented it first?
From the Mozilla perspective the purpose of these changes, except for adding more capabilities for use by web developers, is to lead up to JavaScript 2.0, that is being developed as the next revision of ECMA 262 (revision 4) TC39 workgroup.
Future browsers will support JavaScript 2.0. In the mean time, developers are invited to take advantage of these extra features - natively in Firefox and using JavaScript libraries that provide backward compatibility with Internet Explorer. I find this very useful.
Also, it may be interesting to note that Webkit (the engine developed by KDE and used by Safari, Chrome and several free software browsers) supports JavaScript 1.7.
The biggest reason at the moment for improved JavaScript is for extension writers, who need not worry about cross-browser compatiblity.
JavaScript is a trademark by Sun which was licensed to Netscape and is now held by the Mozilla Foundation. Microsoft has their own implementation of the language called JScript, but there are others (eg. DMDScript).
ECMAScript was an afterthought to add a common baseline to the various implementations. So it's only natural that language development continues outside the standards committee, which is free to add the changes pioneered by the implementors in future revisions of the standard (eg the array extras introduces in JS1.6 will be in ES3.1).