function hardMan(str) { this.queue = [] this.name = str this.queue.push(() => { console.log(this.name); this.next() }); } hardMan.prototype.rest = function (wait) { const func = () => { setTimeout(() => { console.log(`Start learning after ${wait} seconds`) this.next() }, wait * 1000) } this.queue.push(func) return this } hardMan.prototype.restFirst = function (wait) { const func = () => { setTimeout(() => { console.log(`Start learning after ${wait} seconds`) this.next() }, wait * 1000) } this.queue.unshift(func) return this } hardMan.prototype.learn = function (str) { const func = () => { console.log(`Learning ${str}`) } this.queue.push(func) this.next() } hardMan.prototype.next = function () { if (this.queue.length === 0) return const func = this.queue.shift() func() } const HardMan = (name)=>{ return new hardMan("jack"); }