babelConfig.md

title
Babel Config option

ts-jest by default does NOT use Babel. But you may want to use it, especially if your code rely on Babel plugins to make some transformations. ts-jest can call the BabelJest processor once TypeScript has transformed the source into JavaScript.

The option is babelConfig and it works pretty much as the tsconfig option, except that it is disabled by default. Here is the possible values it can take:

• false: the default, disables the use of Babel
• true: enables Babel processing. ts-jest will try to find a .babelrc, .babelrc.js, babel.config.js file or a babel section in the package.json file of your project and use it as the config to pass to babel-jest processor.
• { ... }: inline Babel options. You can also set this to an empty object ({}) so that the default Babel config file is not used.

Examples

Use default babelrc file

/** @type {import('ts-jest').JestConfigWithTsJest} */
module.exports = {
  // [...]
  transform: {
    '<regex_match_files>': [
      'ts-jest',
      {
        babelConfig: true,
      },
    ],
  },
}

import type { JestConfigWithTsJest } from 'ts-jest'

const jestConfig: JestConfigWithTsJest = {
  // [...]
  transform: {
    '<regex_match_files>': [
      'ts-jest',
      {
        babelConfig: true,
      },
    ],
  },
}

export default jestConfig

// OR package.json
{
  // [...]
  "jest": {
    "transform": {
      "<regex_match_files>": [
        "ts-jest",
        {
          "babelConfig": true
        }
      ]
    }
  }
}

Path to a babelrc file

The path should be relative to the current working directory where you start Jest from. You can also use \<rootDir> in the path, or use an absolute path (this last one is strongly not recommended).

/** @type {import('ts-jest').JestConfigWithTsJest} */
module.exports = {
  // [...]
  transform: {
    '<regex_match_files>': [
      'ts-jest',
      {
        babelConfig: 'babelrc.test.js',
      },
    ],
  },
}

import type { JestConfigWithTsJest } from 'ts-jest'

const jestConfig: JestConfigWithTsJest = {
  // [...]
  transform: {
    '<regex_match_files>': [
      'ts-jest',
      {
        babelConfig: 'babelrc.test.js',
      },
    ],
  },
}

export default jestConfig

{
  // [...]
  "jest": {
    "transform": {
      "<regex_match_files>": [
        "ts-jest",
        {
          "babelConfig": "babelrc.test.js"
        }
      ]
    }
  }
}

or importing directly the config file:

/** @type {import('ts-jest').JestConfigWithTsJest} */
module.exports = {
  // [...]
  transform: {
    '<regex_match_files>': [
      'ts-jest',
      {
        babelConfig: require('./babelrc.test.js'),
      },
    ],
  },
}

import type { JestConfigWithTsJest } from 'ts-jest'
import babelConfig from './babelrc.test.js'

const jestConfig: JestConfigWithTsJest = {
  // [...]
  transform: {
    '<regex_match_files>': [
      'ts-jest',
      {
        babelConfig,
      },
    ],
  },
}

export default jestConfig

Inline compiler options

Refer to the Babel options to know what can be used there.

/** @type {import('ts-jest').JestConfigWithTsJest} */
module.exports = {
  // [...]
  transform: {
    '<regex_match_files>': [
      'ts-jest',
      {
        babelConfig: {
          comments: false,
          plugins: ['@babel/plugin-transform-for-of'],
        },
      },
    ],
  },
}

import type { JestConfigWithTsJest } from 'ts-jest'

const jestConfig: JestConfigWithTsJest = {
  // [...]
  transform: {
    '<regex_match_files>': [
      'ts-jest',
      {
        babelConfig: {
          comments: false,
          plugins: ['@babel/plugin-transform-for-of'],
        },
      },
    ],
  },
}

export default jestConfig

{
  // [...]
  "jest": {
    "transform": {
      "<regex_match_files>": [
        "ts-jest",
        {
          "babelConfig": {
            "comments": false,
            "plugins": ["@babel/plugin-transform-for-of"]
          }
        }
      ]
    }
  }
}