• linker {Function}

      • specifier {string} The specifier of the requested module:

        1. import foo from 'foo';
        2. //              ^^^^^ the module specifier

      • referencingModule {vm.Module} The Module object link() is called on.

      • Returns: {vm.Module|Promise}
    • Returns: {Promise}

    Link module dependencies. This method must be called before evaluation, and can only be called once per module.

    The function is expected to return a Module object or a Promise that eventually resolves to a Module object. The returned Module must satisfy the following two invariants:

    • It must belong to the same context as the parent Module.
    • Its status must not be 'errored'.

    If the returned Module‘s status is 'unlinked', this method will be recursively called on the returned Module with the same provided linker function.

    link() returns a Promise that will either get resolved when all linking instances resolve to a valid Module, or rejected if the linker function either throws an exception or returns an invalid Module.

    The linker function roughly corresponds to the implementation-defined [HostResolveImportedModule][] abstract operation in the ECMAScript specification, with a few key differences:

    • The linker function is allowed to be asynchronous while [HostResolveImportedModule][] is synchronous.

    The actual [HostResolveImportedModule][] implementation used during module linking is one that returns the modules linked during linking. Since at that point all modules would have been fully linked already, the [HostResolveImportedModule][] implementation is fully synchronous per specification.

    Corresponds to the [Link() concrete method][] field of [Cyclic Module Record][]s in the ECMAScript specification.