serialize.ts

import { BigNumber } from "bignumber.js";

const serialized: any = {
  blockNumber: "8947598234759823",
  txs: [{ price: "45384238946427" }]
};

class Transaction {
  price: BigNumber;

  constructor(price: BigNumber) {
    this.price = price;
  }

  static fromJSON(json: any) {
    return new Transaction(new BigNumber(json.price));
  }

  toJSON() {
    return {
      price: this.price.toJSON()
    };
  }
}

class Block {
  blockNumber: BigNumber;
  txs: Transaction[];

  constructor(blockNumber: BigNumber, txs: Transaction[]) {
    this.blockNumber = blockNumber;
    this.txs = txs;
  }

  toJSON() {
    return {
      blockNumber: this.blockNumber.toJSON(),
      txs: this.txs.map(tx => tx.toJSON())
    };
  }

  static fromJSON(json: any) {
    return new Block(
      new BigNumber(json.blockNumber),
      json.txs.map((tx: any) => Transaction.fromJSON(tx))
    );
  }
}

const block = Block.fromJSON(serialized);
console.log(block);
console.log(JSON.stringify(block));