## Receive data from a Cairo contract :

When you perform a call, you have the result in an object :

- With a contract.call : `const result=contract.call("read_val", myParameters)`.
- With a contract.meta-class : `const result=contract.read_val(...myParameters)`.

| Type in Cairo | Cairo code | Type expected in JS/TS | JS/TS function to recover data |
| --- | --- | --- | --- |
| felt (251 bits max) | func getV()->(total:felt) | BN | const total:BN = result.total |
|  |  | number (64 bits max) | const total:number = parseInt(result.total) |
|  |  | string representing an hex number | const address:string = number.toHex(result.address) |
| Uint256 (256 bits max) | func getV()->(balance:Uint256) | BN | const balance:BN = uint256.uint256toBN(result.balance) |
| array of felt | func getV()->(list_len:felt, list:felt*) | BN[] | const list:BN[]= result.list |
| shortString (31 ASCII characters max) | func getV()->(title:felt) | string | const title:string = shortString.decodeShortString(result.title) |

Newton

What do I have as the result of a Cairo contract in JavaScript?

Hey this message looks very confusing.
`GatewayError: {'contract_address': ['Expected hex string, got: "0x01C438231cD70f47d1acB8404E51734c1Fb4d79AC55813b3E861fB1EF78Da0D6".']}`

Any hints on this?

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

CairoLang error: `GatewayError: {'contract_address': ['Expected hex string, got: 

Hello! This is day 9 of the 17 days of the Cairo Challenge. And I have no idea how to solve the [playground](https://www.cairo-lang.org/playground/) exercise “Field Elements 2”.  Perhaps you can help me?

```
// As you saw in the previous challenge, the operator '/' does not denote
// truncated (i.e., rounding down) integer division as in other programming
// languages. Instead, one can use library functions such as
// unsigned_div_rem().
//
// Note that unsigned_div_rem() does not work for negative numbers.

%builtins output range_check

// Import unsigned_div_rem() from the math module.
from starkware.cairo.common.math import unsigned_div_rem
from starkware.cairo.common.serialize import serialize_word

func main{output_ptr: felt*, range_check_ptr}() {
    let (q, r) = unsigned_div_rem(value=12, div=3);
    // Output the quotient (12 // 3).
    serialize_word(q);
    // Output the remainder (12 % 3).
    serialize_word(r);

    // Add code that outputs the quotient and remainder of 13 / 3 in addition to 12 / 3 here.

    return ();
}
```

---

> Answers to this question are a part of the ✨ 17 days of Cairo Lang with Playground & Newton. ✨
> 

*Vote for your favorite answer - the best answer will win a $10 award. A new day – a new reward! During the next 17 days, our goal is to attract more developers to the Cairo language and to systematize the knowledge of Cairo lang. [Read rules](https://www.notion.so/17-days-of-Cairo-Lang-with-Newton-550dfcda6a2d449ca468be293c776578)*

How to divide felt in Cairo Lang using unsigned_div_rem?

What’s the difference between Account Abstraction (AA) and Externally Owned Accounts (EOA)?

---

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What’s the difference between Account Abstraction (AA) and Externally Owned Accounts (EOA)?

anybody manged to declare contracts with the new nile?

```
Error: AssertionError: Sender must be passed explicitly when making a direct declaration using --no_wallet.
```

I saw a hardhat issue aswel

must be an upstream thing

https://docs.starknet.io/docs/Blocks/transactions/#calculating-the-hash-of-a-v1-declare-transaction

_This question was originally posted on [StarkNet Discord](https://www.newton.so/view?tags=discord)_

An error “AssertionError: Sender must be passed explicitly when making a direct declaration using —no_wallet.” using the new nile?

What are events in Cairo Language? What purpose do events serve?

Can you explain it so that everyone can understand?

What are events in Cairo Language?

I made an example using [this library with react](https://github.com/fracek/starknet-react-example), everything is working fine in development, but in production, it looks like starknet.js is throwing a type error. You can [open this page](http://starknet-react-example.vercel.app/) to see the error more in detail.

To reproduce locally:

- Clone my example repo
- Build with `yarn run build`
- Serve production build with `yarn run serve`

Based on this [Github thread](https://github.com/0xs34n/starknet.js/issues/37)

How do I use Create React App in StarknetJS?

Can someone explain the difference `between unsigned_div_rem` and `uint256_unsigned_div_rem`?

Why unit version process so many extra steps, but overall number of steps for computing are different for these methods?



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What do I have as the result of a Cairo contract in JavaScript?

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Receive data from a Cairo contract :

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Type in Cairo	Cairo code	Type expected in JS/TS	JS/TS function to recover data
felt (251 bits max)	func getV()->(total:felt)	BN	const total:BN = result.total
		number (64 bits max)	const total:number = parseInt(result.total)
		string representing an hex number	const address:string = number.toHex(result.address)
Uint256 (256 bits max)	func getV()->(balance:Uint256)	BN	const balance:BN = uint256.uint256toBN(result.balance)
array of felt	func getV()->(list_len:felt, list:felt*)	BN[]	const list:BN[]= result.list
shortString (31 ASCII characters max)	func getV()->(title:felt)	string	const title:string = shortString.decodeShortString(result.title)