What is a 'lazy' iterator and why is it important for performance? Give a practical example.

Difficulty: 5/10

iterators, lazy evaluation, performance

A lazy iterator in JavaScript is typically a generator that yields values on demand instead of building a full collection up front. It saves memory and avoids unnecessary work, especially for large or infinite sequences.

Lazy iterators delay computation until values are requested, processing one element at a time. This is critical for large or infinite data sets because it avoids loading everything into memory. For example, a Fibonacci sequence generator using an iterator only computes the next number when next() is called, not all numbers upfront.

Eager evaluation: Compute everything immediately

Lazy evaluation: Compute values on demand

Scenario Questions

0-2 years experience

What is a 'lazy' iterator and why is it important for performance? Give a practical example.

Difficulty: 5/10

iterators, lazy evaluation, performance

A lazy iterator in JavaScript is typically a generator that yields values on demand instead of building a full collection up front. It saves memory and avoids unnecessary work, especially for large or infinite sequences.

Eager evaluation: Compute everything immediately

Lazy evaluation: Compute values on demand

Scenario Questions

0-2 years experience

What is a 'lazy' iterator and why is it important for performance? Give a practical example.

A lazy iterator in JavaScript is typically a generator that yields values on demand instead of building a full collection up front. It saves memory and avoids unnecessary work, especially for large or infinite sequences.

Scenario Questions

What is a 'lazy' iterator and why is it important for performance? Give a practical example.

A lazy iterator in JavaScript is typically a generator that yields values on demand instead of building a full collection up front. It saves memory and avoids unnecessary work, especially for large or infinite sequences.

Scenario Questions

Follow-up Questions