I was refactoring some code, namely organizing the imports (sorting, removing unused, etc.)

I had three files:

1. Controller
2. OverrideService (uses default export)
3. RunService

• Controller depends on both OverrideService & RunService.
• RunService depends on OverrideService

I came across this issue:

In Controller.ts, originally the order of imports was like this:

import { RunService } from '../services/RunService';
import OverrideService from '../services/OverrideService';

When imports were sorted alphabetically the code stopped working properly:

import OverrideService from '../services/OverrideService';
import { RunService } from '../services/RunService';

Giving an error:

TypeError: OverrideService_1.default.overrideDependencyValidator is not a function

When I changed the default export to a named export in OverrideService, and updated the imports to be like this, the issue is no longer there.

import { OverrideService } from '../services/OverrideService';
import { RunService } from '../services/RunService';

I did some research but couldn't find any information on default vs named exports aside from tree-shaking and other irrelevant differences.

What would be the reason a default export cause an issue when reordering imports?