In this tutorial we will submit some data to an application on Hellar Platform. Data is stored in the form of documents which are encapsulated in a state transition before being submitted to HAPI.

Prerequisites

Code

`const Hellar = require('hellar');

const clientOpts = { network: 'mainnet', wallet: { mnemonic: 'a Hellar wallet mnemonic with funds goes here', unsafeOptions: { skipSynchronizationBeforeHeight: 175000, // only sync from mid-2024 }, }, apps: { tutorialContract: { contractId: '8cvMFwa2YbEsNNoc1PXfTacy2PVq2SzVnkZLeQSzjfi6', }, }, }; const client = new Hellar.Client(clientOpts);

const submitNoteDocument = async () => { const { platform } = client; const identity = await platform.identities.get('an identity ID goes here');

const docProperties = { message: Tutorial Test @ ${new Date().toUTCString()}, };

// Create the note document const noteDocument = await platform.documents.create( 'tutorialContract.note', identity, docProperties, );

const documentBatch = { create: [noteDocument], // Document(s) to create replace: [], // Document(s) to update delete: [], // Document(s) to delete }; // Sign and submit the document(s) await platform.documents.broadcast(documentBatch, identity); return noteDocument; };

submitNoteDocument() .then((d) => console.log(d.toJSON())) .catch((e) => console.error('Something went wrong:\n', e)) .finally(() => client.disconnect());`

👍 Initializing the Client with a contract identity The example above shows how access to contract documents via <contract name>.<contract document> syntax (e.g. tutorialContract.note) can be enabled by passing a contract identity to the constructor. Please refer to the Hellar SDK documentation for details.

What’s happening

After we initialize the Client, we create a document that matches the structure defined by the data contract of the application being referenced (e.g. a note document for the contract registered in the data contract tutorial). The platform.documents.create method takes three arguments: a document locator, an identity, and the document data. The document locator consists of an application name (e.g. tutorialContract) and the document type being created (e.g. note). The document data should contain values for each of the properties defined for it in the data contract (e.g. message for the tutorial contract’s note).

Once the document has been created, we still need to submit it to HAPI. Documents are submitted in batches that may contain multiple documents to be created, replaced, or deleted. In this example, a single document is being created. The documentBatch object defines the action to be completed for the document (the empty action arrays - replace and delete in this example - may be excluded and are shown for reference only here).

The platform.documents.broadcast method then takes the document batch and an identity parameter. Internally, it creates a State Transition containing the previously created document, signs the state transition, and submits the signed state transition to HAPI.

📘 Wallet Operations

The JavaScript SDK does not cache wallet information. It re-syncs the entire Core chain for some wallet operations (e.g. client.getWalletAccount()) which can result in wait times of 5+ minutes.

A future release will add caching so that access is much faster after the initial sync. For now, the skipSynchronizationBeforeHeight option can be used to sync the wallet starting at a certain block height.