MediumJavaScript

Your Polling Service Needs a Controllable Repeating Timer With Start, Pause, and Stop

2 views

We are building a Distributed Health Monitoring Dashboard. Our frontend needs to poll various microservice endpoints every 30 seconds to update status lights.

The requirements are specific:

If the user switches tabs, we want to pause polling to save battery and network bandwidth.
If the user logs out, we must stop and completely tear down the timer to prevent memory leaks.
The API must be 'Bulletproof'—calling pause() before start() or calling start() multiple times should not create multiple overlapping intervals (a common bug known as 'Timer Drifting').

The Challenge: Implement a createInterval(callback, interval) utility that returns an object with start, pause, and stop controls. Your solution must ensure that only one interval instance exists at any time and that the state transitions are idempotent.

Language

Sample Test Cases

Case 1

Input

start, wait 350ms at 100ms interval

Expected Output

count===3

Case 2

Input

["function callback() { console.log('Polling...'); }", 100]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 3

Input

["function callback() { return 'executed'; }", 100]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 4

Input

["function callback() { this.count = (this.count || 0) + 1; }", 50]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 5

Input

["function callback() { this.count = (this.count || 0) + 1; }", 50]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 6

Input

pause then start resumes

Expected Output

resumes ticking

Case 7

Input

["function callback() { console.log('Polling...'); }", 1000]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 8

Input

["function callback() { this.log.push('fired'); }", 10]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 9

Input

pause before start

Expected Output

no error

MediumJavaScript

Your Polling Service Needs a Controllable Repeating Timer With Start, Pause, and Stop

2 views

We are building a Distributed Health Monitoring Dashboard. Our frontend needs to poll various microservice endpoints every 30 seconds to update status lights.

The requirements are specific:

If the user switches tabs, we want to pause polling to save battery and network bandwidth.
If the user logs out, we must stop and completely tear down the timer to prevent memory leaks.
The API must be 'Bulletproof'—calling pause() before start() or calling start() multiple times should not create multiple overlapping intervals (a common bug known as 'Timer Drifting').

Language

Sample Test Cases

Case 1

Input

start, wait 350ms at 100ms interval

Expected Output

count===3

Case 2

Input

["function callback() { console.log('Polling...'); }", 100]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 3

Input

["function callback() { return 'executed'; }", 100]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 4

Input

["function callback() { this.count = (this.count || 0) + 1; }", 50]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 5

Input

["function callback() { this.count = (this.count || 0) + 1; }", 50]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 6

Input

pause then start resumes

Expected Output

resumes ticking

Case 7

Input

["function callback() { console.log('Polling...'); }", 1000]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 8

Input

["function callback() { this.log.push('fired'); }", 10]

Expected Output

{"start": "function", "pause": "function", "stop": "function"}

Case 9

Input

pause before start

Expected Output

no error

Your Polling Service Needs a Controllable Repeating Timer With Start, Pause, and Stop

Sample Test Cases

Comments (0)

Your Polling Service Needs a Controllable Repeating Timer With Start, Pause, and Stop

Sample Test Cases

Comments (0)