javascript - Babel file is copied without being transformed

Question

I have this code:

"use strict";

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


let proxy = httpProxy.createProxyServer({});

and I have installed babel-core and babel-cli globally via npm. The point is when I try to compile with this on my terminal:

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

The output file gets copied instead of compiled (I mean, it's the same as the source file).

What am I missing here?

Answer 1

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.