How to use @zilliqa-js/contract - 3 common examples

constructor(subjectStream, stream) {
    if (!subjectStream || !stream) {
      throw new Error('subjectStream and stream is necessary params.')
    }

    // Create instance Proxy provider.
    this.provider = new HTTPProvider(subjectStream, stream)
    // Redefined Wallet to work with user interface.
    this.wallet = new Wallet(subjectStream, stream)
    
    this.blockchain = new Blockchain(this.provider, this.wallet)
    this.contracts = new Contracts(this.provider, this.wallet)
    this.transactions = new TransactionFactory(this.provider, this.wallet)

    this.utils = zilUtils
    this.crypto = {
      fromBech32Address,
      toBech32Address,
      isValidChecksumAddress,
      toChecksumAddress
    }
  }
}

constructor(node: string, websocket: string, provider?: Provider) {
    this.provider = provider || new HTTPProvider(node);
    this.wallet = new Wallet(this.provider);
    this.blockchain = new Blockchain(this.provider, this.wallet);
    this.network = new Network(this.provider, this.wallet);
    this.contracts = new Contracts(this.provider, this.wallet);
    this.transactions = new TransactionFactory(this.provider, this.wallet);
    this.newTxBlockSubscription = new NewTxBlockSubscription(websocket);
  }
}

constructor(node=PROVIDER, provider=new HTTPProvider(PROVIDER)) {
    this.provider = provider || new HTTPProvider(node);
    this.wallet = window.zilPay;
    this.blockchain = new Blockchain(this.provider, this.wallet);
    this.contracts = new Contracts(this.provider, this.wallet);
    this.transactions = new TransactionFactory(this.provider, this.wallet);
    this.utils = zilUtils;
    this.crypto = {
      decodeBase58, encodeBase58,
      fromBech32Address, toBech32Address,
      isValidChecksumAddress, toChecksumAddress
    }
  }
}