Syntax Downgrade and Polyfill

By default, Farm will downgrade to ES5 and inject polyfills automatically in production mode.

note

By default, Farm won't do transformation and inject polyfills for modules under node_modules/, if you need to downgrade syntax and inject polyfills for node_modules/ you can use compilation.presetEnv.include.

Configuring presetEnv

You can use compilation.presetEnv to custom syntax downgrade and polyfill. Using include to add external modules that need to be polyfilled.s

farm.config.ts

export default {
   compilation: {
     presetEnv: {
      // include a package under node_modules
      include: ['node_modules/package-name'],
      options: {
        targets: "Chrome >= 48"
      }
     }
   },
};

By default, Farm will set targets to > 0.25%, not dead. If your project does not require browser compatibility, you can use set a looser value for targets, then less polyfills will be injected and output sizes will be smaller.

Refer to compilation.presetEnv for more options.

With script.target

script.target can also control the target env when generate code. If you want to downgrade your project to ES5, you should set both:

farm.config.ts

export default {
   compilation: {
     script: {
      target: 'ES5'
     },
     presetEnv: {
      // include a package under node_modules
      include: ['node_modules/package-name'],
      options: {
        targets: "> 0.25%, not dead"
      }
     }
   },
};