How to indicate param is optional using inline JSDoc?

After some digging up I found these are ok as well

/**
 * @param {MyClass|undefined}
 * @param {MyClass=}
 * @param {String} [accessLevel="author"] The user accessLevel is optional.
 * @param {String} [accessLevel] The user accessLevel is optional.
 */

Just slightly more visually appealing than function test(/**String=*/arg) {}

From official documentation:

Optional parameter

An optional parameter named foo.

@param {number} [foo]
// or:
@param {number=} foo

An optional parameter foo with default value 1.

@param {number} [foo=1]