Time a function with a helper — practice exercise

What you'll be asked to do

1. 1.Time a function with a helperexercise · easy · 10 min

   Write a timeIt helper and confirm it returns a non-negative duration.

   Passes when: #out should show true.

2. 2.Check the type of the measurementexercise · easy · 10 min · practice plan

   Report the type of what performance.now returns.

   Passes when: #out should show number.

3. 3.Measure twice and compareexercise · easy · 10 min · practice plan

   Run two timings and confirm both completed successfully.

   Passes when: #out should show true.

4. 4.Use console.time safelyexercise · easy · 10 min · practice plan

   Wrap a loop with console.time and confirm it still runs to completion.

   Passes when: #out should show 499500.

5. 5.Collect several measurementsexercise · medium · 10 min · practice plan

   Time the same block three times and confirm all are valid.

   Passes when: #out should show 3.

6. 6.Fix Date.now used where more precision helpsbug fix · easy · 8 min

   performance.now is designed specifically for timing code, and reports fractions of a millisecond.

   Passes when: #out should show timed with performance.now.

7. 7.Fix the subtraction done backwardsbug fix · easy · 8 min · practice plan

   The start time must be subtracted from the end, not the reverse.

   Passes when: #out should show 250 ms measured.

8. 8.Fix the function never actually calledbug fix · easy · 8 min · practice plan

   The timer wraps a call that never happens, so the loop never runs.

   Passes when: #out should show 499500.

9. 9.Fix console.timeEnd given a different labelbug fix · easy · 8 min · practice plan

   The label passed to timeEnd must match the one given to time, or the timer is never closed.

   Passes when: #out should show timer closed.

10. 10.Fix only one measurement takenbug fix · easy · 8 min · practice plan

    A single measurement can be noisy; several give a better picture.

    Passes when: #out should show 3.

Between them these tasks cover performance.now, Timing helpers and Repeated measurement.

Looking for a different chapter? See every practice set, or switch to the interview theory questions.