Compiler option

The compiler option allows you to define the compiler to be used. It'll be used to load the NodeJS module holding the TypeScript compiler.

The default value is typescript, which will load the original TypeScript compiler module. The loaded version will depend on the one installed in your project.

If you use a custom compiler, such as ttypescript, make sure its API is the same as the original TypeScript, at least for what ts-jest is using.

Example

JavaScript

// jest.config.js
/** @type {import('ts-jest').JestConfigWithTsJest} */
module.exports = {
  // [...]
  transform: {
    // '^.+\\.[tj]sx?$' to process ts,js,tsx,jsx with `ts-jest`
    // '^.+\\.m?[tj]sx?$' to process ts,js,tsx,jsx,mts,mjs,mtsx,mjsx with `ts-jest`
    '^.+\\.tsx?$': [
      'ts-jest',
      {
        compiler: 'ttypescript',
      },
    ],
  },
}

TypeScript

// jest.config.ts
import type { JestConfigWithTsJest } from 'ts-jest'

const jestConfig: JestConfigWithTsJest = {
  // [...]
  transform: {
    // '^.+\\.[tj]sx?$' to process ts,js,tsx,jsx with `ts-jest`
    // '^.+\\.m?[tj]sx?$' to process ts,js,tsx,jsx,mts,mjs,mtsx,mjsx with `ts-jest`
    '^.+\\.tsx?$': [
      'ts-jest',
      {
        compiler: 'ttypescript',
      },
    ],
  },
}

export default jestConfig

JSON

// package.json
{
  // [...]
  "jest": {
    "transform": {
      // '^.+\\.[tj]sx?$' to process ts,js,tsx,jsx with `ts-jest`
      // '^.+\\.m?[tj]sx?$' to process ts,js,tsx,jsx,mts,mjs,mtsx,mjsx with `ts-jest`
      "^.+\\.tsx?$": [
        "ts-jest",
        {
          "compiler": "ttypescript"
        }
      ]
    }
  }
}