SearchMap: A JavaScript Map with searchable keys

SearchMap.js

/** Evaluates an array, makes the key lowercasee and makes the value an object with original keyname
 * @param  {Array} iterable=[] an array of arrays:[[key,val],[key,val]]
 * @returns Array
 */
function LowercaseIterable(iterable = []) {
	if (iterable.length === 0) return [];

	const newIterable = iterable.map(([key, val]) => {
		const entry = [
			key.toLowerCase(),
			{ originalKeyName: key, value: val }
		];
		return entry;
	});

	return newIterable;
}

/**
 * @extends Map
 * @classdesc Makes it possible to do a case insensitive search of a map by key
 * @namespace SearchableKeyMap
 * @property {Map} originalMap the original, unchanged map
 */
class SearchableKeyMap extends Map {
	/**
	 * @param {Iterable} iterable an array of arrays: [[key,val], [key,val]]
	 */
	constructor(iterable) {
		super(LowercaseIterable(iterable));
		this.originalMap = new Map(iterable);
	}

	/** Determines if any of SearchableKeyMap's keys contain a substring
	 * @param  {string} searchKey
	 *
	 * @returns {Boolean}
	 */
	containsKey(searchKey) {
		const searchKeyName = searchKey.toLowerCase();
		const entries = this.entries();
		let result = false;
		let nextEntry = entries.next();

		while (!nextEntry.done) {
			const key = nextEntry.value[0];

			if (key.includes(searchKeyName)) {
				result = true;
				break;
			}

			nextEntry = entries.next();
		}

		return result;
	}

	/** Searches in a map for a single key containing a substring
	 * @param  {string} searchKey
	 *
	 * @returns string. First result it finds
	 */
	getKeyContaining(searchKey) {
		const searchKeyName = searchKey.toLowerCase();
		const entries = this.entries();
		let result;
		let nextEntry = entries.next();

		while (!nextEntry.done) {
			const [key] = nextEntry.value;

			if (key.includes(searchKeyName)) {
				result = key;
				break;
			}

			nextEntry = entries.next();
		}

		return result;
	}

	/** Searches for keys in a map that contain a substring	 *
	 * @param  {string} searchKey
	 *
	 * @returns array
	 */
	getKeysContaining(searchKey) {
		const result = [];
		const searchKeyName = searchKey.toLowerCase();
		const entries = this.entries();
		let nextEntry = entries.next();

		while (!nextEntry.done) {
			const [key] = nextEntry.value;

			if (key.includes(searchKeyName)) {
				result.push(key);
			}

			nextEntry = entries.next();
		}

		return result;
	}

	/** Creates a SearchableKeyMap of keys based on a search string
	 * @param  {string} keyName key to search for
	 *
	 * @returns SearchableKeyMap
	 */
	mapFromKeysContaining(keyName) {
		if (!keyName) throw new Error('Keyname not provided');

		const newMap = new SearchableKeyMap();
		const searchKeyName = keyName.toLowerCase();
		const keys = this.getKeysContaining(searchKeyName);

		keys.forEach((key) => {
			const { originalKeyName, value } = this.get(key);
			newMap.set(originalKeyName, value);
		});

		return newMap;
	}
}