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Create Lamden Transactions

Create Transaction Info Object

This object will describe the transaction you are going to send

//Sender and Receiver public keys
let senderVk = "ea2cee33f9478d767d67afe345592ef36446ee04f8d588fa76942e6569a53298"
let receiverVk = "bb0fab41b9118f0afdabf3721fa9a6caae3c93845ed409d3118841065ad1a197"

let txInfo = {
contractName: "currency",
methodName: "transfer",
kwargs: { // the method arguements
to: receiverVk, // string
amount: {"__fixed__":"1000.5"} // fixed object required for float values
stampLimit: 50, //Max stamps to be used. Could use less, won't use more.

Create transaction

Create a Transaction Builder instance

Learn about creating a networkInfo object

let tx = new Lamden.TransactionBuilder(networkInfo, txInfo)

Send transaction

let senderSk = "69a8db3fb7196debc2711fad1fa1935918d09f5d8900d84c3288ea5237611c03"
// Specify a maternode URL here to direct the tx to a specific node. Setting this to undefined will use the nodes from the Network object
let masternodeURL = undefined

tx.send(senderSk, masternodeURL, (res, err) => {
if (err) throw new Error(err)
.then(res => console.log(res))

//or'response', (response) => {
if (tx.resultInfo.type === 'error') return
tx.send(senderSk).then(() => tx.checkForTransactionResult())

Returns the NEW changed state in the currency contract for whatever variables the transfer method effected.
In this case, the new balances for both keys is returned

state_changes: {
"currency:balances:ea2cee33f9478d767d67afe345592ef36446ee04f8d588fa76942e6569a53298": "4895.0" // -1005 (amount + stamps)
"currency:balances:bb0fab41b9118f0afdabf3721fa9a6caae3c93845ed409d3118841065ad1a197": "1000.0" // +1000
status_code: 0
stamps_used: 19

Getting a Nonce and Processor

Nonce and processor will be retrieved from the masternode automatcially when send() is called.

getNonce() can be used to set the nonce and processor before hand.

let tx = new Lamden.TransactionBuilder(networkInfo, TxInfo)

tx.getNonce((res, err) => {
if (err) console.log("Nonce Not Set")
else console.log(res)

"nonce": 37,
"processor": "0000000000000000000000000000000000000000000000000000000000000000",
"sender": "ea2cee33f9478d767d67afe345592ef36446ee04f8d588fa76942e6569a53298"

Transaction Builder Class

Class Members

  • uid (string): txInfo.uid || txData.uid
    • A unique identifier for this tx.
    • Used for keeping track of transactions
  • sender (string): txInfo.senderVk
    • The transaction sender's vk
  • contract (string): txInfo.contractName
    • The smartcontract to transact against
  • method (string): txInfo.methodName
    • The method or function that will be called on the smartcontract
  • kwargs (string): txInfo.kwargs
    • The arguement values that will be sent to the method
    • default {}
  • stampLimit (string): txInfo.stampLimit
    • The stamps to be supplied to the transaction
    • This is the upper limit the transaction is allowed to use
    • The transaction could use less stamps
    • The transation will fail if the processing of the transaction causes it to clock more stamps then this value.
    • The sender's wallet must have at least the amount of TAU that would equale the stamp value, even if the transaction won't take that many stamps to complete. This means you cannot simply send 1,000,000 as the stampLimit for each transaction.
  • nonce (integer): txInfo.nonce if exists || txData.nonceResult.nonce if exists
    • transaction nonce value
    • default undefined
    • Set with getNonce();
  • processor (integer): txInfo.processor if exists || txData.nonceResult.processor if exists
    • transaction processor
    • default undefined
    • Set with getNonce();
  • nonceMasternode (string):
    • The masternode the nonce was retrieved from
    • default undefined
  • signature (string):
    • The transaction signature
    • Set with sign();
    • Automatically set when send(<sk>) is executed
  • transactionSigned (boolean):
    • If the transaction has been signed or not
    • default false
  • nonceResult (object): txData.nonceResult
    • If the transaction has been signed or not
  • txSendResult (object): txData.txSendResult
    • The raw response from the masternode as a result of calling send()
  • txBlockResult (object): txData.txBlockResult
    • The block result returned from the masternode as a result of a processed transaction
    • Created from txCheckResult after parsing for errors
  • txHash (string): txData.txSendResult.hash
    • Transaction hash set as a result of calling send()
    • Only set if the transaction was accepted by the network
  • resultInfo (object): txData.resultInfo
    • Current state of the transaction
    • Updated during each phase of the transaction process
  • txCheckResult (object):
    • The raw response from the masternode as a result of calling checkForTransactionResult()
    • could contain errors
  • txCheckAttempts (integer):
    • How many times the masternode has been checked for a transaction result
  • txCheckLimit (integer):
    • The amount of times to check for a transaction result before failing
  • payload (object):
    • The transaction payload before sorting
  • sortedPayload (object):
    • The transaction payload after sorting
    • This is what will actually be signed and sent in the transaction
  • tx (object):
    • The completed and signed tx object to be sent

Constructor( networkInfo, txInfo, txData)

Creates an instance of TransactionBuilder


  • networkInfo (object): required
  • txInfo (object): required
  • txData (object): optional
    • The output from getAllInfo() can be used to hydrate a new Transaction Builder object from a previous object


  • Sets `payload'
  • Calls sortObject() to set sortedPayload using payload as input


  • Sets tx
  • Creates tx.metadata.signature using signature
  • Creates tx.metadata.timestamp using current datetime in seconds
  • Createa tx.payload from sortedPayload.orderedObj


Validates the signature of the transaction

Returns boolean: valid signature

Throws error: If sign() has not previously been called.


Signs the payload of a transaction

  • Sets signature
  • Sets transactionSigned to true


  • sk (string): required
    • secret/private key of the sender wallet

Throws error: If sk has not been provided

sortObject( object )

Sorts the keys and array values in an object recursivly. This is required because while verifying the signature of the transaction the blockchain will sort the payload in the same way.


  • object (object): required
    • An object to be sorted

Returns object:

"orderedObj": // The sorted object
"json": // the sorted object as a JSON string

aync getNonce( callback )

Get the current nonce and processor for the sender wallet.

  • Calls makePayload()
  • Sets nonceResult
  • Sets nonce
  • Sets processor
  • Sets nonceMasternode

getNonce() is called during the send() process and doesn't need to be called beforhand unless needed for some other reason.


  • callback (object): optional

Returns Promise: Resolves to Nonce Information object

"nonce": // current nonce
"processor": // current processor
"sender": // sender vk
"masternode": // url of the masternode the nonce was recieved from
"timestamp": // The date/time Lamden-js attempted to get the nonce

aync send( sk, masternode, callback )

Send a transaction.

  • Calls getNonce() if nonce is undefined

  • Calls sign() if transactionSigned is false

  • Calls makeTransaction()

  • Calls API.sendTransaction()

  • Calls handleMasterNodeResponse

  • Sets txSendResult


  • sk (string): optional if previously signed
    • The secret/private key of the sender wallet
    • Used to sign the transaction before sending
  • masternode (string): optional
    • default nonceMasternode
    • Provide a specific masternode to send the transaction to
  • callback (function): optional

Returns Promise: Resolved to

Masternode Transaction Response


{ errors: // Array of errors }

Emits response: Masternode Transaction Response

Throws error: if transaction is unsigned and no sk provided

Throws error: forwards erros from all methods called while completing the transaction process

aync checkForTransactionResult( callback )

Checks the blockchain for a result to the txHash returned by send().

  • Calls API.checkTransaction()

  • Calls handleMasterNodeResponse

  • Sets txCheckAttempts

  • Sets txCheckResult

Returns Promise: Resolved to

Masternode Transaction Details


{ errors: // Array of errors }

Emits response: Masternode Transaction Details

handleMasterNodeResponse(result, callback)

Parses the masternode return objects to determine the state of the transaction.



Updates the status of the transaction to pending if the Masternode Transaction Response contained a hash property.

  • Sets resultInfo

Returns object:

title: 'Transaction Pending',
subtitle: 'Your transaction was submitted and is being processed',
message: `Tx Hash: ${this.txHash}`,
type: 'success',

setBlockResultInfo( result )

Parses the Masternode Transaction Details object for errors and creates the final version of resultInfo from the results of parsing.

  • Sets resultInfo