lib.syntax#

• Type:

type EcmaScriptVersion =
  | 'es5'
  | 'es6'
  | 'es2015'
  | 'es2016'
  | 'es2017'
  | 'es2018'
  | 'es2019'
  | 'es2020'
  | 'es2021'
  | 'es2022'
  | 'es2023'
  | 'es2024'
  | 'esnext';

type Syntax = EcmaScriptVersion | string[];

• Default: 'esnext'

Configure the syntax to which JavaScript and CSS will be downgraded.

See Output Compatibility - Syntax Downgrade for more details.

Set ECMAScript Version#

You can set the ECMAScript version directly, such as es2015, es2022, etc.

export default {
  lib: [
    // ...
  ],
  syntax: 'es2015',
};

Set Browserslist Query#

You can also set the Browserslist query, such as last 2 versions, > 1%, node >= 16, chrome >= 80, etc.

export default {
  lib: [
    // ...
  ],
  syntax: ['last 2 versions', '> 1%'],
};

Mix ECMAScript Version and Browserslist Query#

You can also mix ECMAScript version and Browserslist query, such as es2015 and node 20. We will turn ECMAScript Version into Browserslist query, and then merge them together.

export default {
  lib: [
    // ...
  ],
  syntax: ['es2015', 'node 20'],
};