Transpiling a Node.js + TypeScript app with Babel: why it's not using optional chaining?

Question

I am experimenting with Babel to understand better how it works. I created a simple API with Node.js and TypeScript. Everything works fine when I transpile code and the server runs properly. I have a question though: in node v14.15.3 optional chaining is supported, so why when I build with:

rm -rf build/ && babel src --source-maps --extensions '.js,.ts,.tsx' --ignore '**/*.test.ts' -d build

no matter what version of node I'm running in the shell (by using nvm - v12.18.3 or v14.15.3) the following line

console.log(x?.ciao ?? 10)

it's always transpiled to

console.log((_x$ciao = x === null || x === void 0 ? void 0 : x.ciao) !== null && _x$ciao !== void 0 ? _x$ciao : 10);

I would expect it to use .? and ?? in the transpiled code since they're supported. What am I missing?

I also tried to remove the @babel/preset-typescript preset and did a test with a single file, but yet the code is transpiled as above.

My .babelrc file:

{
  "presets": ["@babel/preset-typescript", ["@babel/preset-env", { "shippedProposals": true }]],
  "plugins": [
    [
      "module-resolver",
      {
        "root": "./src",
        "alias": {
          "@root": ["./"],
          "@src": ["./src"]
        },
        "extensions": [".js", ".ts"]
      }
    ]
  ],
  "sourceMaps": true
}

the point of babel is to compile code that works in browsers, it's re-writing the code like that so that it's backwards-compatible — the_cuaz
– the_cuaz, Commented Dec 30, 2020 at 5:00

devamat · Accepted Answer · 2020-12-31 02:05:51Z

0

To make it work use "targets": { "node": 14 } as in the following .babelrc example. This will not transpile .? or ?? since they are supported in node 14.x.

{
  "presets": [
    "@babel/preset-typescript",
    [
      "@babel/preset-env",
      {
        "targets": { "node": 14 }
      }
    ]
  ],
  "plugins": [
    [
      "module-resolver",
      {
        "root": "./src",
        "alias": {
          "@root": ["./"],
          "@src": ["./src"]
        },
        "extensions": [".js", ".ts"]
      }
    ]
  ],
  "sourceMaps": true
}

answered Dec 31, 2020 at 2:05

devamat

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