Yashotantra Academy logo
← JavaScript theorytheory 0/50 · 0%
level 1
Curious · 0 XP
streak
0d
perfect
0
badges
0

100 XP to Apprentice

Data · easy

6. Arrays and Iteration

map, filter, reduce and for...of.

1 min read3 questionsup to 50 XPtopic 6/50

Read in another language

AI translates the explanation and quiz text while preserving code and answer scoring.

`map` transforms each element, `filter` selects subsets, `reduce` folds to a single accumulator, and `for...of` enables `await` inside loops.

js
const fees = [21000, 45000, 60000];
const total = fees.reduce((a, b) => a + b, 0);

How to study this topic

  1. 1. Read the explanation once end to end, skipping the code.
  2. 2. Re-read the code snippets and say out loud what each line does.
  3. 3. Answer the quiz without scrolling back — that is the real check.
  4. 4. Read every explanation, even for the answers you got right.

Scoring

  • · Up to 30 XP from quiz accuracy.
  • · +15 XP for a perfect first attempt.
  • · +5 XP while a 3-day streak is running.
  • · 75% or higher marks the topic complete.

Check your understanding

  1. 1. Which method folds an array to one value?

  2. 2. Which loop cleanly supports `await` per iteration?

  3. 3. What does array.map() return?

Badges

First light
Pass your first topic
Sharp shooter
3 perfect first-try quizzes
On a roll
Study 3 days in a row
Week warrior
Study 7 days in a row
Grinder
Earn 500 XP
Deep diver
Earn 1500 XP