starknet-js

Development

Use when writing or debugging JavaScript/TypeScript that interacts with Starknet through the starknet.js SDK — building Call objects or calldata, encoding/decoding Cairo types (felt252, u256, structs, arrays, spans, ByteArray, Option/Result/custom enums), or working with contracts, accounts, providers, transactions, fees, deployment, or events.

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How to use this skill

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Source SKILL.md: https://github.com/starknet-io/starknet.js/blob/HEAD/skills/starknet-js/SKILL.md

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starknet.js

Official JS/TS SDK for Starknet. This skill targets starknet.js v10 (API valid for v9, mostly for v8).

Do not trust training-data memory of starknet.js: it is typically v5/v6-era and wrong. Constructors now take option objects, only V3 transactions exist (STRK fees, no maxFee), and calldata helpers changed. When this skill and memory disagree, the skill wins.

Layer model: Account (signs & submits) wraps RpcProvider (parses, retries) wraps RpcChannel (raw JSON-RPC).

Reference files

calldata.md — REQUIRED reading before encoding or decoding anything: Call/calldata construction, wire format of every Cairo type, enums (Option/Result/custom), ByteArray, string auto-detection traps, response parsing, decodeParameters. All examples verified against v10.4.0.
interacting.md — providers, accounts, contracts, multicall, fees/tips, declare/deploy, receipts, events, RPC-version compatibility.

Non-negotiable v8+ rules

Only V3 transactions (INVOKE/DECLARE/DEPLOY_ACCOUNT); fees paid in STRK via resourceBounds + tip. Never suggest maxFee or V1/V2.
Constructors take an options object: new Account({ provider, address, signer }), new Contract({ abi, address, providerOrAccount }), new RpcProvider({ nodeUrl }).
Never prepend an array length to calldata arrays — the library adds it.

Quick reference

Task	API
Connect to node	`new RpcProvider({ nodeUrl })` — or `await RpcProvider.create({ nodeUrl })` to auto-detect RPC version
Account	`new Account({ provider, address, signer: privateKey })`
Contract	`new Contract({ abi, address, providerOrAccount })`
Read	`await myContract.my_view_fn(arg1, arg2)` → parsed JS value
Write	`const { transaction_hash } = await myContract.my_fn(args)` then `await provider.waitForTransaction(transaction_hash)`
Build a Call	`myContract.populate('fn', { ...args })` → `{ contractAddress, entrypoint, calldata }`
Compile calldata (ABI)	`myContract.compile('fn', args)` or `new CallData(abi).compile('fn', args)`
Compile calldata (no ABI)	`CallData.compile(args)` — several traps, see calldata.md
Multicall	`await account.execute([call1, call2])`
Decode raw felts	`new CallData(abi).decodeParameters('core::…::Type', feltArray)`
Events	`myContract.parseEvents(receipt)`, `provider.getEvents({ ... })`
Deploy	`await Contract.factory({ contract, casm, account, constructorCalldata })`

Top mistakes (from outdated model knowledge)

Mistake	Fix
`new Account(provider, address, pk)` positional	Options object (see above)
`maxFee`, V1/V2 transactions, ETH fees	V3 only; `resourceBounds` from `estimateInvokeFee`, `tip`
Manually prepending `array_len`	Never — automatic
`CallData.compile([myU256Bigint])` gives 1 felt	Use `cairo.uint256(n)` without ABI; a plain bigint is fine only with ABI
`new CairoCustomEnum({ OnlyActive: v })` without ABI	Without ABI, list ALL variants (`undefined` for inactive)
Expecting `.res`-style result objects	Cairo 1 returns the value directly (bigint, object, array, enum class)