TSConfig

Modern browsers support all ES6 features, so ES6 is a good choice. You might choose to set a lower target if your code is deployed to older environments, or a higher target if your code is guaranteed to run in newer environments.

The target setting changes which JS features are downleveled and which are left intact. For example, an arrow function () => this will be turned into an equivalent function expression if target is ES5 or lower.

Changing target also changes the default value of lib. You may “mix and match” target and lib settings as desired, but you could just set target for convenience.

For developer platforms like Node there are baselines for the target, depending on the type of platform and its version. You can find a set of community organized TSConfigs at tsconfig/bases, which has configurations for common platforms and their versions.

The special ESNext value refers to the highest version your version of TypeScript supports. This setting should be used with caution, since it doesn’t mean the same thing between different TypeScript versions and can make upgrades less predictable.