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

100 XP to Apprentice

Web3 · hard

40. Contract Events and Log Parsing

Bloom filters, indexed topics, and log decoding.

1 min read3 questionsup to 50 XPtopic 40/50

Read in another language

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

Solidity events are logged on-chain. Indexed parameters become searchable 32-byte topics (`topics[1..3]`), while non-indexed parameters are ABI-encoded in the log data field.

js
const filter = contract.filters.Transfer(userAddress);
const logs = await contract.queryFilter(filter, fromBlock, toBlock);

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. What happens to indexed event arguments in Solidity logs?

  2. 2. What is the maximum number of indexed topics an event can have?

  3. 3. Why must log querying be paged across block ranges?

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