Method shift

jsonrpc/src/linkedMap.ts:101–113

()

	}

	public shift(): V | undefined {
		if (!this._head && !this._tail) {
			return undefined;
		}
		if (!this._head || !this._tail) {
			throw new Error('Invalid list');
		}
		const item = this._head;
		this._map.delete(item.key);
		this.removeItem(item);
		this._size--;
		return item.value;
	}

	public forEach(callbackfn: (value: V, key: K, map: LinkedMap<K, V>) => void, thisArg?: any): void {
		let current = this._head;