Simple middleware implementation

middleware.js

/**
 * @template Context
 * @callback Handler
 * @param {Context} context 
 * @param {function(): void} next 
 */

/**
 * @template Context
 * @example
 * const middleware = new Middleware([firstHandler, secondHandler]);
 * middleware.handle(someObject)
 */
class Middleware {
	/**
	 * @param {Handler<Context>[]} handlers
	 */
	constructor(handlers) {
		this.handlers = handlers;
	}

	/** @param {Context} context */
	handle(context) {
		let index = 0;

		const next = () => {
			if (index >= this.handlers.length) {
				return;
			}

			index++;

			this.handlers[index](context, next);
		}

		next();
	}
}

Example

const middleware = new Middleware([firstHandler, secondHandler]);
const string = "hello world";
middleware.handle(string)

/** @type {Handler<string>} */
function firstHandler(context, next) {
	next();
}
/** @type {Handler<string>} */
function secondHandler(context, next) {
	next();
}