substrate-knowledge-map

Quiz 6: Polkadot JS API

Overview

This quiz covers the following parts of the Substrate Knowledge Map:

• Polkadot JS API

1. What are the differences between Polkadot-JS Apps and Polkadot-JS API? Check all that apply.

• Polkadot-JS Apps provides a front-end UI and wallet to interact with Substrate-based networks.
• Polkadot-JS API is the official JS API that connects to Substrate-based networks.
• Polkadot-JS API is the official front-end UI to interact with any Substrate-based chain.
• Polkadot-JS API, in addition to Substrate-based networks, can also connect to other mainstream blockchains such as Bitcoin and Ethereum.

2. In Polkadot-JS API, what datatype is used to represent a number (i.e. u64, i64, u128, i128) on a Substrate network?

• The default data type Number in javascript.
• String
• bn.js
• bignumber.js
• decimal.js

3. What is the correct way to query a storage value in a Substrate network and subscribe to its changes?

• const val = await api.query.my_pallet.storage
• const unsub = await api.query.my_pallet.storage(value => {...})
• const val = await api.consts.my_pallet.const
• const val = await api.tx.my_pallet.tx().signAndSend()
• const val = await api.tx.my_pallet.tx().signAndSend(value => {...})

4. Assuming that you don’t need to subscribe to the on-chain transaction status, what is the proper way to send an extrinsic to a Substrate network?

• const val = await api.query.my_pallet.storage
• const unsub = await api.query.my_pallet.storage(value => {...})
• const val = await api.consts.my_pallet.const
• const val = await api.tx.my_pallet.tx().signAndSend()
• const val = await api.tx.my_pallet.tx().signAndSend(value => {...})