# E0310: optional parameter cannot have both '?' and initializer; remove '?'

In TypeScript, parameters can be explicitly marked as optional with `?`. It is a syntax error to write a default initializer for a parameter marked optional with `?`:

    async function download(uri, options? = {}) {
      /* ... */
    }

Parameters with default initializers are always optional. To fix this syntax error, remove the redundant `?`:

    async function download(uri, options = {}) {
      /* ... */
    }

Introduced in quick-lint-js version 2.10.0.

Documentation for other errors