# fund

Funds a Bitcoin transaction.

# Type

(
  tx: NakamotoJS.Transaction,
  opts?: {
    include?: string[]
    exclude?: string[]
  }
): Promise<void>

# Parameters

# `tx`

A NakamotoJS transaction object or a Bitcoin Computer Transaction object (that the object from Bitcoin Computer extends the object from NakamotoJS).

# `opts`

An optional object can be passed as parameter to include or exclude certain UTXOs. When using include, the transaction will be funded with the UTXOs specified as the first inputs.

Key	Description	Default Value
include	UTXOs to include	`[]`
exclude	UTXOs to exclude	`[]`

UTXOs are encoded as <transaction-id>:<output-number>.

# Return Value

If the wallet does not have sufficient funds, an error is thrown.

# Example

import { Computer } from '@bitcoin-computer/lib'
import { address, networks, Transaction } from '@bitcoin-computer/nakamotojs'
import { chain, network, url } from '../../utils'

// Create wallet
const computer = new Computer({ chain, network, url })

describe('fund', () => {
  before('Fund wallet', async () => {
    await computer.faucet(1e8)
  })

  it('Should fund a NakamotoJS transaction', async () => {
    // Build a transaction with NakamotoJS
    const tx = new Transaction()
    const { regtest } = networks
    const outputScript = address.toOutputScript('mkHS9ne12qx9pS9VojpwU5xtRd4T7X7ZUt', regtest)
    tx.addOutput(outputScript, BigInt(1e5))

    // Fund, sign and broadcast transaction
    await computer.fund(tx)
    await computer.sign(tx)
    await computer.broadcast(tx)
  })

  it('Should fund a Bitcoin Computer transaction', async () => {
    // Build a transaction with the Bitcoin Computer library
    const { tx } = await computer.encode({
      exp: `class C extends Contract {}; new C()`,
      fund: false,
    })

    // Fund, sign and broadcast transaction
    await computer.fund(tx)
    await computer.sign(tx)
    await computer.broadcast(tx)
  })
})

Sources