no-unsupported-features.md

node/no-unsupported-features

disallow unsupported ECMAScript features on the specified version

• ⛔ This rule has been deprecated. Use node/no-unsupported-features/es-syntax and node/no-unsupported-features/es-builtins instead.

⚠️ This is deprecated since v7.0.0. Use node/no-unsupported-features/es-syntax and node/no-unsupported-features/es-builtins instead.

Node.js doesn't support all ECMAScript standard features. This rule reports when you used unsupported ECMAScript 2015-2018 features on the specified Node.js version.

※ About ECMAScript 2018, this rule reports only features which have arrived at stage 4 until 2018-02-01. It needs a major version bump in order to cover newer features.

📖 Rule Details

⚠️ This rule expects to be used with the following configuration:

{
    "env": {"es6": true},
    "parserOptions": {"ecmaVersion": 2018}
}

⚠️ This rule reads the engines field of package.json to detect Node.js version.

I recommend a use of the engines field since it's the official way to indicate what Node.js versions your module is supporting. For example of package.json:

{
    "name": "your-module",
    "version": "1.0.0",
    "engines": {
        "node": ">=6.0.0"
    }
}

If the engines field is omitted, this rule chooses 4 since it's the minimum version the community is maintaining.

Examples of 👎 incorrect code for this rule:

/*eslint node/no-unsupported-features: ["error", {version: 4}]*/
/*eslint-env es6*/

function foo(a = 1) {  /*error Default Parameters are not supported yet on Node v4.*/
    //...
}

function foo(...a) {   /*error Rest Parameters are not supported yet on Node v4.*/
    //...
}

var a = [...b];        /*error Spread Operators are not supported yet on Node v4.*/
var a = /foo/y;        /*error RegExp 'y' Flags are not supported yet on Node v4.*/
var a = /foo/u;        /*error RegExp 'u' Flags are not supported yet on Node v4.*/
var {a, b} = c;        /*error Destructuring are not supported yet on Node v4.*/
var {a, b} = c;        /*error Destructuring are not supported yet on Node v4.*/

let a = 1;             /*error 'let' Declarations in non-strict mode are not supported yet on Node v4.*/
const a = 1;           /*error 'const' Declarations in non-strict mode are not supported yet on Node v4.*/
class A {}             /*error Classes in non-strict mode are not supported yet on Node v4.*/

if (a) {
    function foo() {   /*error Block-Scoped Functions in non-strict mode are not supported yet on Node v4.*/
        //...
    }
}

var p = new Proxy(o, { /*error Proxy is not supported yet on Node v4.*/
    //...
});

Examples of 👍 correct code for this rule:

/*eslint node/no-unsupported-features: ["error", {version: 4}]*/
/*eslint-env es6*/

for (var a of list) {
    //...
}

var a = `hello, ${world}!`;

function foo() {
    "use strict";

    let a = 1;
    const b = 2;

    class A {
        //...
    }

    if (c) {
        function bar() {
            //...
        }
    }
}

var p = new Promise((resolve, reject) => {
    //...
});

Options

{
    "node/no-unsupported-features": ["error", {
        "version": 4,
        "ignores": []
    }]
}

version

As mentioned above, this rule reads the engines field of package.json to detect Node.js version. Also, you can overwrite the version by version option. The version option accepts the following version number:

• 0.10
• 0.12
• 4
• 5
• 6
• 6.5 ... Symbol.hasInstance and Symbol.species.
• 7 ... Exponential operators, Object.values, Object.entries, and Object.getOwnPropertyDescriptors.
• 7.6 ... Async functions.
• 8 ... Trailing commas in functions.
• 8.3 ... Rest/Spread proeprties.
• 9.0 ... Illegal escape sequences in taggled templates, RegExp 's' flags, RegExp lookbehind assertions, SharedArrayBuffer, and Atomics.
• 10.0 ... RegExp named capture groups, RegExp Unicode property escapes, Async generators, and for-await-of loops.

ignores

If you are using transpilers, maybe you want to ignore the warnings about some features. You can use this ignores option to ignore the given features. The "ignores" option accepts an array of the following strings.

• "syntax" (group)
  • "defaultParameters"
  • "restParameters"
  • "spreadOperators"
  • "objectLiteralExtensions"
  • "forOf"
  • "binaryNumberLiterals"
  • "octalNumberLiterals"
  • "templateStrings"
  • "regexpY"
  • "regexpU"
  • "destructuring"
  • "unicodeCodePointEscapes"
  • "new.target"
  • "const"
  • "let"
  • "blockScopedFunctions"
  • "arrowFunctions"
  • "generatorFunctions"
  • "classes"
  • "modules"
  • "exponentialOperators"
  • "asyncAwait"
  • "trailingCommasInFunctions"
  • "templateLiteralRevision"
  • "regexpS"
  • "regexpNamedCaptureGroups"
  • "regexpLookbehind"
  • "regexpUnicodeProperties"
  • "restProperties"
  • "spreadProperties"
  • "asyncGenerators"
  • "forAwaitOf"
• "runtime" (group)
  • "globalObjects" (group)
    • "typedArrays" (group)
      • "Int8Array"
      • "Uint8Array"
      • "Uint8ClampedArray"
      • "Int16Array"
      • "Uint16Array"
      • "Int32Array"
      • "Uint32Array"
      • "Float32Array"
      • "Float64Array"
      • "DataView"
    • "Map"
    • "Set"
    • "WeakMap"
    • "WeakSet"
    • "Proxy"
    • "Reflect"
    • "Promise"
    • "Symbol"
    • "SharedArrayBuffer"
    • "Atomics"
  • "staticMethods" (group)
    • "Object.*" (group)
      • "Object.assign"
      • "Object.is"
      • "Object.getOwnPropertySymbols"
      • "Object.setPrototypeOf"
      • "Object.values"
      • "Object.entries"
      • "Object.getOwnPropertyDescriptors"
    • "String.*" (group)
      • "String.raw"
      • "String.fromCodePoint"
    • "Array.*" (group)
      • "Array.from"
      • "Array.of"
    • "Number.*" (group)
      • "Number.isFinite"
      • "Number.isInteger"
      • "Number.isSafeInteger"
      • "Number.isNaN"
      • "Number.EPSILON"
      • "Number.MIN_SAFE_INTEGER"
      • "Number.MAX_SAFE_INTEGER"
    • "Math.*" (group)
      • "Math.clz32"
      • "Math.imul"
      • "Math.sign"
      • "Math.log10"
      • "Math.log2"
      • "Math.log1p"
      • "Math.expm1"
      • "Math.cosh"
      • "Math.sinh"
      • "Math.tanh"
      • "Math.acosh"
      • "Math.asinh"
      • "Math.atanh"
      • "Math.trunc"
      • "Math.fround"
      • "Math.cbrt"
      • "Math.hypot"
    • "Symbol.*" (group)
      • "Symbol.hasInstance"
      • "Symbol.isConcatSpreadablec"
      • "Symbol.iterator"
      • "Symbol.species"
      • "Symbol.replace"
      • "Symbol.search"
      • "Symbol.split"
      • "Symbol.match"
      • "Symbol.toPrimitive"
      • "Symbol.toStringTag"
      • "Symbol.unscopables"
    • "Atomics.*" (group)
      • "Atomics.add"
      • "Atomics.and"
      • "Atomics.compareExchange"
      • "Atomics.exchange"
      • "Atomics.wait"
      • "Atomics.wake"
      • "Atomics.isLockFree"
      • "Atomics.load"
      • "Atomics.or"
      • "Atomics.store"
      • "Atomics.sub"
      • "Atomics.xor"
  • "extends" (group)
    • "extendsArray"
    • "extendsRegExp"
    • "extendsFunction"
    • "extendsPromise"
    • "extendsBoolean"
    • "extendsNumber"
    • "extendsString"
    • "extendsMap"
    • "extendsSet"
    • "extendsNull"

If a group value is given, all sub items of the value are ignored. e.g. if "String.*" is given then "String.raw" and "String.fromCodePoint" are ignored.

Examples of 👍 correct code for the "ignores" option:

/*eslint node/no-unsupported-features: ["error", {version: 4, ignores: ["defaultParameters"]}]*/
/*eslint-env es6*/

function foo(a = 1) {
    //...
}

⚠️ Known Limitations

This rule cannot report non-static things. E.g., a use of instance methods.

📚 Further Reading

• http://node.green/

🔎 Implementation

• Rule source
• Test source