These eight implementation questions combine API design with edge behavior. You will implement a cancelable debounce, a trailing throttle, ordered promise aggregation, a cycle-aware clone, structural equality, a typed event emitter, generic currying, and a payload-aware state machine. Every utility has a limited, explicit contract.
State that contract before you optimize. For a clone, say which data types are supported. For equality, say whether key order matters. For timing, trace exact-boundary calls against the supplied logical clock. For promises, handle an empty list and preserve input positions even when completion order differs. Compiler assertions protect the generic relationships as well as the runtime test fixtures. These are original interview practice scenarios, without employer attribution or copied question statements.
class Clock {now=0;private next=0;private jobs=new Map<number,{at:number;fn:()=>void}>();set(fn:()=>void,delay:number):number {const id=++this.next;this.jobs.set(id,{at:this.now+delay,fn});return id;}clear(id:number|undefined):void {if(id!==undefined)this.jobs.delete(id);}tick(until:number):void {for(;;){const ready=[...this.jobs].filter(([,job])=>job.at<=until).sort((a,b)=>a[1].at-b[1].at || a[0]-b[0]);if(!ready.length)break;const [id,job]=ready[0];this.now=job.at;this.jobs.delete(id);job.fn();}this.now=until;}}
function debounce<A extends unknown[]>(fn:(...args:A)=>void,wait:number,clock:Clock){let id:number|undefined;let last:A|undefined;const call=(...args:A)=>{last=args;clock.clear(id);id=clock.set(()=>{id=undefined;const current=last;last=undefined;if(current)fn(...current);},wait);};return Object.assign(call,{cancel(){clock.clear(id);id=undefined;last=undefined;},flush(){clock.clear(id);id=undefined;const current=last;last=undefined;if(current)fn(...current);}});}
function solve(value:string):string[] {const x=JSON.parse(value) as {wait:number;end:number;calls:[number,string][]};const clock=new Clock();const out:string[]=[];const handler=debounce((label:string)=>out.push(clock.now+":"+label),x.wait,clock);for(const [at,label] of x.calls){clock.tick(at);if(label==="CANCEL")handler.cancel();else if(label==="FLUSH")handler.flush();else handler(label);}clock.tick(x.end);return out;}
A complete implementation for the first scenario; trace its input before editing.