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Node.js plans to support import/export ES6 (ECMAScript 2015) modules
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Just wonder how do we import a module in node.js 8 - are we still using require?
Or do we still need babel for using import?
I have been digging around but seems no answer. If we still have to use require, why can't node implement import yet?
UPDATE-2018.11.15 ↓
Short answer
We're still using require
Long answer
ESM loading has partially landed in node 8.5.0 which was released in September 2017. As such, it has beeen part of the specs as an experimental feature for a little while: see the API documentation here. Caveats include the need for the --experimental-modules flag and the use of a new .mjs extension for modules.
There is still changes that need to happen in V8 before ESM loading is stable and fully featured so as with my original answer, I would still advise on sticking with CommonJS require if you don't already use Babel for other stuff
See this post for a more didactic explanation
PREVIOUS ANSWER ↓
The two implementations are completely different under the hood, so there is more to it than what meets the eyes
The takeaway is that there are still lingering issues/questions over the specifications (all the way to V8), and as such import cannot currently be implemented in Node without a using a transpiler
See this comment (dated February 2017) from one of the contributor:
At the current point in time, there are still a number of specification and implementation issues that need to happen on the ES6 and Virtual Machine side of things before Node.js can even begin working up a supportable implementation of ES6 modules. Work is in progress but it is going to take some time — We’re currently looking at around a year at least.
Keep in mind that transpilers simply converts the ES6 module syntax to the CommonJS module syntax, so there is currently no performance benefits. In other words, if you don't have a Babel pipeline already, there is not much incentives to create one just to use the new proposed import syntax, except from a proactive syntactic perspective
For more details on how the implementation differs, see this write up
Related
TypeScript supports Node's ECMAScript module resolution with the node16 and nodenext module and moduleResolution options. It's not clear if I must use Node 16 or greater to use either option. Node 14 has support for ESM and not much changed between 14 and 16. Experimentally TypeScript works as expected with Node 14 and node16 but maybe there are edge cases that I'm not aware of.
https://www.typescriptlang.org/docs/handbook/esm-node.html
The 16.0.0 change log lists a few removals and deprecations but no new features or changes to module resolution. I don't think these changes would affect typescript.
(SEMVER-MAJOR) module: remove module.createRequireFromPath (Antoine du Hamel) #37201
(SEMVER-MAJOR) module: runtime deprecate subpath folder mappings (Antoine du Hamel) #37215
(SEMVER-MAJOR) module: runtime deprecate "main" index and extension lookups (Antoine du Hamel) #37206
(SEMVER-MAJOR) module: runtime deprecate invalid package.json main entries (Antoine du Hamel) #37204
(SEMVER-MAJOR) process: runtime deprecate changing process.config (James M Snell) #36902
Regarding features support, you can take a look at this matrix to verify that what you need works as expected. Regarding module support when you take a look at the documentation of NodeJS, some New features have been added like in V16.17 but it seems that compatibility is an important matter; moreover a breaking change would be indeed in the logs like the ones you mentionned above. Node 16.17 is a LTS so stability is of greater concern than intermediates. Hope that helps !
When I first saw this question, I thought this was a simple "yes, you need to use Node 16 with this." After doing initial research, that answer became foggy, but after lookin gat this SO post, it again seems that you need to use Node 16 with node16 and nodenext.
Node 14 has support for ESM and not much has changed between 14 and 16.
I believe that since they have added that support, patches pushed for Node 10 and 12 have also allowed support for it, so that may change they way we approach this question.
In the end, I still believe that using Node 16 is the best option for you.
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I am looking to working on a project using node js addons with C++. I came across two abstract library NAN and N-API that I can use. However I am unable to decide which one I should use. I was not able to find proper comparison between these two libraries.
What are the pros, cons and differences of both? How to choose between them?
So far I have found that NAN has more online tutorials/articles regarding async calls. But N-API is officially supported by Node (and was created after NAN as a better alternative, although not sure.)
My understanding is this:
The Node-API (formerly N-API) was added to the core node.js interface in v8.0.0. "It is intended to insulate Addons from changes in the underlying JavaScript engine…" to quote the documentation. It also provides some other wrappers around things like buffers and asynchronous work (which should help avoid some of the underlying non-stable APIs noted in their Implications of ABI stability section).
nan (Native Abstractions for Node) is indeed older and so also supports older versions of node.js — back to node.js 0.8! Now despite its author claiming back in 2017:
As I mentioned somewhere else, N-API is not meant to be directly used for anything. Where has this notion come from? It is an (effectively internal) low-level infrastructure layer meant to offer ABI stability. There will be another layer on top.
…I do not see much warning to that effect in the official Node.js add-on documentation. Perhaps this other comment is a bit more insightful:
Yes, you should still use NAN for production use. It covers every relevant version of Node.js. Also note that N-API is not intended for end users. You should eventually use https://github.com/nodejs/node-addon-api.
Again, that was in June of 2017 by the maintainer of nan at the time. It seems that node-addon-api has matured in the meantime and remains active. In fact, I found a comment in the -addon-api repo that is only a month old at present:
…part of the goal was to make it easy to transition from nan.
So I think the answer is:
use nan if you want something mature and very backwards-compatible
use node-addon-api if you want something forwards-looking in C++
use Node-API/N-API if you are comfortable working in C and dealing with possible lower-level concerns
You should use the node-addon-API module for new C++ code (or N-API for C code). All supported (non-EOL) versions of Node.js support it, and it makes maintaining and distributing native add-ons much easier: whereas addons using NAN require rebuilding the module for each NODE_MODULE_VERSION (major version of Node.js), modules using N-API/Node-Addon-API are forward-compatible:
A given version n of N-API will be available in the major version of Node.js in which it was published, and in all subsequent versions of Node.js, including subsequent major versions.
There's a somewhat confusing compatibility matrix here. N-API version 3 is compatible with Node.js v8.11.2+, v9.11.0+ and all later major versions (v10+), for example.
On top of that, node-addon-API fixes a lot of the annoying parts of NAN (like Buffers always being char* instead of, say uint8_t*).
NAN still works of course, and there are more learning resources online, but node-addon-API is the way forward.
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Everyone these days is forcing typescript. There are so many fans and articles about it. Angular team is making their framework in TS.
But my experience with migrating ES6 to TS was very disappointing.
I tried to migrate our relatively fresh codebase (writen in ES6) to Typescript last month and faced a ton of pitfalls!
To be clear, we are talking about node.js application with mocha unit tests and ESLint configured (using babel to transpile).
First of all, to empower type checking I set up noImplicitAny option,
got hundreds of errors and fixed it. But after that, I got typing errors due to typescript does not understand some node.js predefined modules, like stream (The problem is actually bigger, due to lack of typings for a lot of modules).
After that, I installed typings - recommended replacement for tsd tool for manage library d.ts files, but it's node typing definition , while resolving stream problem, added a lot of errors because it duplicates some predefined types.
In addition, I found out that typescript actually does not compile many features of ES6 into ES5 actually, such as generators.
It forced me to make complex build process (TS -> (typescript) ES6 -> (babel) ES5), and it means that I have to waste my original source maps.
All above took a lot of time to configure.
So, I'm confused. I really love the idea behind typescript, but implementation seems so rude to me. I hope I'm wrong.
Maybe someone who used Typescript in real project, not HelloWorld one, could explain me what am I doing wrong?
I set up noImplicitAny option
You have very high expectations. For a better experience while migrating a project from ES6, just don't use this option.
I got typing errors due to typescript does not understand some node.js predefined modules, like stream.
The JS libraries that don't have type definitions are a pain. But the implicit type any will save you.
After that, I installed typings […] added a lot of errors because it duplicates some predefined types.
Exclude the browser directory and browser.d.ts from your tsconfig.json.
In addition, i found out that typescript does not compile many features of ES6 to ES5 actually, such as generators. It forces me to made complex build process (TS -> (typescript) ES6 -> (babel) ES5), and it means that I have to waste my original source maps.
It's the design choice that makes TS really robust: the compiled code doesn't need any runtime library.
But why do you use Babel on your generated ES6 code? With Node.js 4 or 5, your ES6 code will work fine.
Is typescript robust enough?
As much as the JavaScript VM are.
TypeScript with the target ES6 on Node.js
Since TS 1.7, the option --module can be used in association with the target es6. Example, in tsconfig.json:
"compilerOptions": {
"module": "commonjs",
"target": "es6",
}
NB: Since TS 1.8, modules are emitted with a "use strict"; prologue.
Node.JS v0.11.3 claims to have support for ECMAScript 6 modules with the flag --harmony_modules.
I have tried various examples, such as the following.
module math {
export var pi = 3.141593;
}
What is the syntax to get modules working in Node.JS?
The modules implementation in V8 is incomplete. There's parsing support when enabled with --harmony-modules, but support of the actual functionality was put on hold. The reason for this is because the specification for how ES6 modules will actually work has been in the works and is still not fully nailed down.
The implementation in Continuum (the linked screenshot from Crazy Train's answer) dates back to an interim spec from November 2012 and is now woefully out of date because of the ongoing changes to the ES6 module's spec. This is why the V8 devs put development of support for modules on hold.
It seems like the modules spec is approaching stability (though I expect we'll see small refinements for a while) and I think (hope at least) that we'll see SpiderMonkey and V8 moving forward with implementations over the next 6 months.
Useful links:
V8 modules bug: https://code.google.com/p/v8/issues/detail?id=1569
SpiderMonkey modules bug: https://bugzilla.mozilla.org/show_bug.cgi?id=harmony%3Amodules
You can use Continuum, which is an ES6 virtual machine written in (current) JavaScript.
So I want to program a module, but I want it to work with Node's require/module.exports system AND ES6 export keyword. I'm wondering if there is either
a conditional expression which would allow me to ascertain "Who is asking for this module, require() or import?" or
a way of implementing BOTH module.exports and export without Node#0.10+ freaking out about the export keyword.
This is primarily so my code is both compatible with current useable technology and will be backwards compatible after the ES6 switch later this year. Additionally, I am teaching my co-workers to program in JS and want to help them learn to make their code modular. Since we are so close to the ES6 switch, it would be easier to teach them one, mostly inclusive, way than teaching them 2 ways and requiring they just remember when to use each. If the answer is, "There is no way," I will just have to teach them one and add the other as a minor side note.
As always, Thank you all for any help you might provide. Have a wonderful day.