What are the possible side-effects in javascript?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of JavaScript conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
A side effect is the modification of the state through the invocation of a function or expression. These side effects make our function impure by default. Below are some side effects which make function impure,
- Making an HTTP request. Asynchronous functions such as fetch and promise are impure.
- DOM manipulations
- Mutating the input data
- Printing to a screen or console: For example, console.log() and alert()
- Fetching the current time
- Math.random() calls: Modifies the internal state of Math object
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.