Class Block

src/blockchain.js:75–139

}

class Block {
  /**
   * @param {number} timestamp
   * @param {Transaction[]} transactions
   * @param {string} previousHash
   */
  constructor(timestamp, transactions, previousHash = '') {
    this.previousHash = previousHash;
    this.timestamp = timestamp;
    this.transactions = transactions;
    this.nonce = 0;
    this.hash = this.calculateHash();
  }

  /**
   * Returns the SHA256 of this block (by processing all the data stored
   * inside this block)
   *
   * @returns {string}
   */
  calculateHash() {
    return crypto
      .createHash('sha256')
      .update(
        this.previousHash +
          this.timestamp +
          JSON.stringify(this.transactions) +
          this.nonce
      )
      .digest('hex');
  }

  /**
   * Starts the mining process on the block. It changes the 'nonce' until the hash
   * of the block starts with enough zeros (= difficulty)
   *
   * @param {number} difficulty
   */
  mineBlock(difficulty) {
    while (
      this.hash.substring(0, difficulty) !== Array(difficulty + 1).join('0')
    ) {
      this.nonce++;
      this.hash = this.calculateHash();
    }

    debug(`Block mined: ${this.hash}`);
  }

  /**
   * Validates all the transactions inside this block (signature + hash) and
   * returns true if everything checks out. False if the block is invalid.
   *
   * @returns {boolean}
   */
  hasValidTransactions() {
    for (const tx of this.transactions) {
      if (!tx.isValid()) {