src/vs/editor/contrib/suggest/suggestMemory.ts/PrefixMemory/toJSON
class PrefixMemory:	toJSON(): object {

		let entries: [string, MemItem][] = [];
		this._trie.forEach((value, key) => entries.push([key, value]));

		// sort by last recently used (touch), then
		// take the top 200 item and normalize their
		// touch
		entries
			.sort((a, b) => -(a[1].touch - b[1].touch))
			.forEach((value, i) => value[1].touch = i);

		return entries.slice(0, 200);
	}