VSCode and jsDoc definitions for classes in other files

Question

I am super confused about how Intellisense works - sometimes it's "automagic" and sometimes I can never get it to work.

Here's an example where I just can't get it to work:

// item.js

export default class Item {
    /**
     * Creates an Item
     * @param {string} type The item type
     */
    constructor(type) {
        this.type = type;
    }

    /**
     * Logs the type of this item
     */
    outputType() {
        console.log(this.type);
    }
}

// itemlist.js

import Item from './item';

export default class ItemList {
    /**
     * Makes an item list
     * @type {string[]} items The types of the items to generate
     */
    constructor(items) {
        /**
         * @type {Item[]}
         */
        this.items = items.map(i => new Item(i));
    }
}

In the above example, in itemlist.js, Intellisense does not know that this.items should be treated as a list of Item objects, and therefore does not autosuggest class properties or methods when I type something like:

this.items[0].

Not even this works in itemlist.js:

const item = new Item('simple');
item.

^ in the above examples there are no Intellisense suggestions for "outputType" or anything related to the item.