HZhzoo·Jul 11, 2017
The purpose of https://github.com/babel/babel-preset-env is that it handles all this automatically (not run when it's supported natively)
In ECMAScript 2017 Language Specificationbabel
babel-preset-env
JavaScript2016–2017
babel / babel-preset-env · Archived
babel-preset-env
PSA: this repo has been moved into babel/babel -->
3Distinct people
16Mentions
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PSA: this repo has been moved into babel/babel -->
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This week on Hacker News
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HN mentions by month16 dated mentions
Observed mentions: 2016-10-18 19:09:39 UTC to 2017-07-11 19:03:29 UTC.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| Oct 2016 | 2016-10-01 00:00:00 UTC | 2016-11-01 00:00:00 UTC | 4 | 0 | 4 |
| Nov 2016 | 2016-11-01 00:00:00 UTC | 2016-12-01 00:00:00 UTC | 1 | 0 | 1 |
| Dec 2016 | 2016-12-01 00:00:00 UTC | 2017-01-01 00:00:00 UTC | 5 | 1 | 4 |
| Jan 2017 | 2017-01-01 00:00:00 UTC | 2017-02-01 00:00:00 UTC | 0 | 0 | 0 |
| Feb 2017 | 2017-02-01 00:00:00 UTC | 2017-03-01 00:00:00 UTC | 3 | 0 | 3 |
| Mar 2017 | 2017-03-01 00:00:00 UTC | 2017-04-01 00:00:00 UTC | 0 | 0 | 0 |
| Apr 2017 | 2017-04-01 00:00:00 UTC | 2017-05-01 00:00:00 UTC | 0 | 0 | 0 |
| May 2017 | 2017-05-01 00:00:00 UTC | 2017-06-01 00:00:00 UTC | 1 | 0 | 1 |
| Jun 2017 | 2017-06-01 00:00:00 UTC | 2017-07-01 00:00:00 UTC | 1 | 0 | 1 |
| Jul 2017 | 2017-07-01 00:00:00 UTC | 2017-08-01 00:00:00 UTC | 1 | 0 | 1 |
What Hacker News says
16 sourcesYeah a good idea. I was thinking we could make a similar table to compat-table (maybe using six-speed or this) that we could use as data to https://github.com/babel/babel-preset-env so that Babel could compile based on the compiled speed relative to native support. Haven't really looked into in much yet (if anyone is interested, let me know)
Basically, if there is native support but it's not as fast as compiled/polyfilled we could continue to compile.
In JSC loves ES6You don't have to use Babel, but if you want to use newer/syntax not in Node/v8 then yes. Always a tradeoff, but gave a talk at TC39 recently about this, https://github.com/hzoo/role-of-babel-in-js, https://twitter.com/left_pad/status/867593358977499137.
https://github.com/babel/babel-preset-env with our `"node": "current"` option can help with this.
In V8, Advanced JavaScript, and the Next Performance Frontier [video]We don't support custom syntax that isn't already a proposal (meaning it has potential to be in JS), and we also encourage using presets like https://github.com/babel/babel-preset-env instead of providing your own configuration of plugins unless you are more of a power user.
It's our intention as a tool to align with TC39 and transition users to using native JS when it's supported
In Announcing TypeScript 2.2The purpose of Babel/transpilers is to eventually allow users to use the native versions of language features. Native support will eventually be faster (not at first), will result in less code sent to users (compiled code is larger), and easier to debug (don't need sourcemaps).
https://v8project.blogspot.com/2017/02/high-performance-es20...
I made https://github.com/babel/babel-preset-env to make it easier to transition. Hoping that Babel makes it easier to not have to think about whether you are using native or not, so we'll work on that workflow.
In ECMAScript 2016+ in FirefoxYep and with Babel we recommend using https://github.com/babel/babel-preset-env to compile only what's missing in the targets you support.
Hopefully we have a better solution about making multiple bundles (separate one for IE) soon
In ECMAScript 2016+ in Firefoxhttps://github.com/babel/babel-preset-env/ should help with this to remove the polyfills that are already supported, and with some future work to remove polyfills are unused.
In Ask HN: If you targetting ES6 by default, how did you rationalize that choice?Might be a good chance to suggest using our new preset: https://github.com/babel/babel-preset-env/.
TL;DR - automate your Babel config options based on targets.
babel-preset-env: A Babel preset that can automatically determine the Babel plugins and polyfills you need based on your supported environments.
It takes the data from compat-table [1] to generate a mapping [2] between a Babel plugin and the first version that a browser/env supports. We calculate the least common denominator of your targeted envs to determine the final set of plugins to compile with.
(Feel free to ask questions, I help maintain Babel and the preset). Just released a 1.0 a few weeks ago and looking for more help and usage! Looking into more help with removing unnecessary polyfills, and determining plugins based on performance via benchmarks of native/compiled.
And
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yes there is a lot of work that goes into making this work correctly (and in the foreseeable future with ES2015+). Would appreciate any help moving forward. And maybe we should just replace/recommend this preset instead of anything else to fight the fatigue..
[1]: https://kangax.github.io/compat-table/es6/
[2]: https://github.com/babel/babel-preset-env/blob/master/data/p...
Show HN: Babel-preset-env, auto determines required Babel plugins based on env
3 points · Open discussionThey're getting better at describing which features are shimmed, but the easiest way to check is by running a single plugin on a bit of code and seeing for yourself.
For instance, I decided just now to check if `transform-object-rest-spread` included an Object.assign polyfill (because spread syntax transpiles to Object.assign behind the scenes.)
With the following input:
var foo = { x: 1, y: 2 };
var bar = { a: 3, b: 4, ...foo };
var baz = new Promise(function(resolve, reject) {
resolve("quux");
});
I get the following output
var _extends = Object.assign || function (target) { for (var i = 1; i < arguments.length; i++) { var source = arguments[i]; for (var key in source) { if (Object.prototype.hasOwnProperty.call(source, key)) { target[key] = source[key]; } } } return target; };
var foo = { x: 1, y: 2 };
var bar = _exte
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nds({ a: 10, b: 11 }, foo);
var baz = new Promise(function(resolve, reject) {
resolve("quux");
});
The problem here, (to borrow phrasing from the docs) is that "Babel uses very small helpers for common functions such as _extend. By default this will be added to every file that requires it. This duplication is sometimes unnecessary, especially when your application is spread out over multiple files."
To solve this problem, many people use the `transform-runtime` plugin [1] as well. To put it shortly, it replaces inline helper functions (like _extends in the example above) with imports from an adapter module called 'babel-runtime', which itself exposes the relevant polyfills (regenerator[2] and core-js[3]).
With `transform-runtime`, I get the following:
import _Promise from "babel-runtime/core-js/promise";
import _extends from "babel-runtime/helpers/extends";
var foo = { x: 1, y: 2 };
var bar = _extends({ a: 10, b: 11 }, foo);
var baz = new _Promise(function (resolve, reject) {
resolve("foo");
});
Notice that the Promise implementation was polyfilled as well.
> I didn't know how to tell Babel which browsers I was targeting...
You might *really like babel-preset-env[4], a new project they just launched. Basically, you give it a set of browser targets (much like autoprefixer) and it works out exactly which plugins you need to support the latest (currently es2015, I think) version of javascript.
Hope that helps! Sorry for going on a Babel-related spiel in a Typescript thread, couldn't help myself. ;)
1: http://babeljs.io/docs/plugins/transform-runtime/#technical-...
2: https://facebook.github.io/regenerator/
3: https://github.com/zloirock/core-js
4: https://github.com/babel/babel-preset-env
You might be interested in https://github.com/babel/babel-preset-env :D.
(I'm working on it so let me know if you have questions)
In Announcing TypeScript 2.1I believe that's a goal of https://github.com/babel/babel-preset-env. There are also a few manually crafted presets on npm which target a particular environment and EcmaScript version, e.g. https://github.com/blockai/babel-preset-eslatest-node6 (I'm the author).
In Async/await support in FirefoxFor those using Babel already or want to use ES6+ on a set of supported browsers: we have started work on https://github.com/babel/babel-preset-env. Would appreciate more testing!
It allows passing in a set of supported browsers and transpiling what is required using the lowest common denominator env (uses https://github.com/kangax/compat-table for data).
// .babelrc with preset options
{
"presets": [
["env", {
"targets": {
"chrome": 52,
"ie": 11,
"browsers": ["last 2 versions", "safari 7"]
}
}]
]
}
If you have questions, ask below (or make an issue)
In Overview of JavaScript ES6 featuresWorking on https://github.com/babel/babel-preset-env right now which should help with this
In Overview of JavaScript ES6 featuresYou can use node specific preset like other's have mentioned but working on https://github.com/babel/babel-preset-env for all future versions as well
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