Interview retrospect - Frontend Engineer

Intreview retrospect of Javascript engineer

Interview retrospect

Technical backgroudn

Garbage Collection

Avoid Garbage, optimized memory management way

Coding Questions

Implement cache memory, limited sized

For find way to manage the VM’s memory. It’s quite important manage de-reference of unused variables, objects.

Implement bind function

Function.prototype.bind()

Handle multiple async

let fn1 = (cb) => { setTimeout(() => { console.log("10"); cb(); }, 10); };
let fn2 = (cb) => { setTimeout(() => { console.log("50"); cb(); }, 50); };
let fn3 = (cb) => { setTimeout(() => { console.log("20"); cb(); }, 20); };
let fn4 = (cb) => { setTimeout(() => { console.log("30"); cb(); }, 30); };
let done = () => { console.log("done"); };

let fnArr = [fn1, fn2, fn3, fn4];

// start from fn1, fn2, fn3, f4
// 1. print like
/*
10
50
20
30
done
*/
function printSeries(fns) {
  // TODO:
}
printSeries(fnArr);
// 2. print like
/*
10
20
30
50
done
*/
function printParallel(fns) {
  // TODO:
}

Answer is

function printSeries(fns) {
  if (fns === undefined || !fns.length) {
    done();
    return;
  }  
  let fn = fns[0];
  fn(() => printSeries(fns.slice(1)));
}

function printParallel(fns) {
  let fnToPromise = (fn) => new Promise((res)=> fn(res));
  let promises = fns.map(fnToPromise);
  Promise.all(promises).then(done);
}

You can check by live HERE