How can I use meta-class of contract (starknetjs) for interaction?

Use meta-class of Contract:

Besides read/write contract memory, you have another way to interact with a contract: the meta-class: each Contract object has specific functions to interact with. For example, here, we have 2 additional functions for the Test contract object :

• Contract.get_balance
• Contract.increase_balance

The code can be modified this way :

//initialize Provider 
const provider = new Provider({ sequencer: { network: "goerli-alpha" } });
// connect your account. To adapt to your own account :
const privateKey0 = process.env.OZ_ACCOUNT_PRIVATE_KEY;
const account0Address = "0x123....789";

const starkKeyPair0 = ec.getKeyPair(privateKey0);
const account0 = new Account(provider, account0Address, starkKeyPair0);

// Connect the deployed Test contract in Tesnet
const testAddress = "0x5f7cd1fd465baff2ba9d2d1501ad0a2eb5337d9a885be319366b5205a414fdd";
  // read abi of Test contract
const { abi: testAbi } = await provider.getClassAt(testAddress);
if (testAbi === undefined) { throw new Error("no abi.") };
const myTestContract = new Contract(testAbi, testAddress, provider);
// Connect account with the contract
myTestContract.connect(account0);
// Interactions with the contract with call & invoke
const bal1 = await myTestContract.get_balance();
console.log("Initial balance =", bal1.res.toString());
const resu = await myTestContract.increase_balance(10, 30);
await provider.waitForTransaction(resu.transaction_hash);
const bal2 = await myTestContract.get_balance();import { Provider, Contract, Account, ec, json } from "starknet";
console.log("Initial balance =", bal2.res.toString());