Babel 文件不经过转换即可复制

我有这个密码:

"use strict";


import browserSync from "browser-sync";
import httpProxy from "http-proxy";


let proxy = httpProxy.createProxyServer({});

我已经通过 npm 在全球范围内安装了 babel-core和 babel-cli。关键在于，当我在终端上尝试用它编译时:

babel proxy.js --out-file proxified.js

输出文件被复制而不是编译(我的意思是，它与源文件相同)。

我错过了什么？

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最佳答案

Babel is a transformation framework. Pre-6.x, it enabled certain transformations by default, but with the increased usage of Node versions which natively support many ES6 features, it has become much more important that things be configurable. By default, Babel 6.x does not perform any transformations. You need to tell it what transformations to run:

npm install babel-preset-env

and run

babel --presets env proxy.js --out-file proxified.js

or create a .babelrc file containing

{
"presets": [
"env"
]
}

and run it just like you were before.

env in this case is a preset which basically says to compile all standard ES* behavior to ES5. If you are using Node versions that support some ES6, you may want to consider doing

{
"presets": [
["env", { "targets": { "node": "true" } }],
]
}

to tell the preset to only process things that are not supported by your Node version. You can also include browser versions in your targets if you need browser support.

小开 
npm install --save-dev babel-preset-node5


npm install --save-dev babel-preset-react

...and then creating a .babelrc with the presets:

{
"presets": [
"node5",
"react"
]
}

...resolved a very similar issue for me, with babel 3.8.6, and node v5.10.1

https://www.npmjs.com/package/babel-preset-node5
https://www.npmjs.com/package/babel-preset-react

小开

I had the same problem with a different cause:

The code I was trying to load was not under the package directory, and Babel does not default to transpiling outside the package directory.

I solved it by moving the imported code, but perhaps I could have also used some inclusion statement in the Babel configuration.

小开

First ensure you have the following node modules:

npm i -D webpack babel-core babel-preset-es2015 babel-preset-stage-2 babel-loader

Next, add this to your Webpack config file (webpack.config.js) :

// webpack.config.js
...
module  :  {
loaders  :  [
{
test    :  /\.js$/,
loader  :  'babel',
exclude :  /node_modules/,
options :  {
presets  :  [ 'es2015', 'stage-2' ] // stage-2 if required
}
}
]
}
...

References:

Good Luck!

小开

Same error, different cause:

Transpiling had worked before and then suddenly stopped working, with files simply being copied as is.

Turns out I opened the .babelrc at some point and Windows decided to append .txt to the filename. Now that .babelrc.txt wasn't recognized by babel. Removing the .txt suffix fixed that.

小开

fix your .babelrc

{
"presets": [
"react",
"ES2015"
]
}
小开

In year 2018:

Install following packages if you haven't yet:

npm install babel-loader babel-preset-react

webpack.config.js

{
test: /\.jsx?$/,
exclude: /node_modules/,
use: [
{
loader: 'babel-loader',
options: {
presets: ['es2015','react']  // <--- !`react` must be part of presets!
}
}
],
}
小开

Ultimate solution

I wasted 3 days on this 

import react from 'react' unexpected identifier

I tried modifying webpack.config.js and package.json files, and adding .babelrc, installing & updating packages via npm, I've visited many, many pages but nothing has worked.

What worked? Two words: npm start. That's right.

run the 

npm start

command in the terminal to launch a local server

...

(mind that it might not work straight away but perhaps only after you do some work on npm because before trying this out I had deleted all the changes in those files and it worked, so after you're really done, treat it as your last resort)

I found that info on this neat page. It's in Polish but feel free to use Google translate on it.

小开

Most of these answers are obsolete. @babel/preset-env and "@babel/preset-react are what you need (as of July 2019).

小开

As of 2020, Jan:

STEP 1: Install the Babel presets:

yarn add -D @babel/preset-env @babel/preset-react

STEP 2: Create a file: babelrc.js and add the presets:

module.exports = {
// ...
presets: ["@babel/preset-env", "@babel/preset-react"],
// ...
}

STEP 3:- Install the babel-loader:

yarn add -D babel-loader

STEP 4:- Add the loader config in your webpack.config.js:

{
//...
module: [
rules: [
test: /\.(js|mjs|jsx|ts|tsx)$/,
loader: require.resolve('babel-loader')
]
]
//...
}

Good Luck...


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