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Examples

This document describes how to interact with ICON Network using JavaScript SDK. This document contains SDK installation, API usage guide, and code examples.
This document is focused on serving the following groups.
  • Web Developer using JavaScript as the main language
  • Web Developer who wants to make dApp using ICON Network
This document is focused on how to use icon-sdk-js properly. If you would like to know about the details of icon-sdk-js API, see official icon-sdk-js API Reference document.
Get different types of examples as follows. Complete source code is found on Github at https://github.com/icon-project/icon-sdk-js/tree/master/quickstart​
Example
Description
​Wallet​
An example of creating and loading a keywallet.
An example of transferring ICX and confirming the result.
An example of deploying an IRC token, transferring the token and confirming the result.
An example of checking block confirmation and printing the ICX and token transfer information.

Installation

Usage in Node.js

Install icon-sdk-js module using npm.
npm install --save icon-sdk-js
Import icon-sdk-js module.
const IconService = require('icon-sdk-js');

Usage in browser

Install icon-sdk-js module using npm,
npm install --save icon-sdk-js
or using CDN.
<script src="https://cdn.jsdelivr.net/gh/icon-project/[email protected]/build/icon-sdk-js.web.min.js"></script>
Then, import icon-sdk-js module.
import IconService from 'icon-sdk-js';

Usage in react-native environment

Install icon-sdk-js module using npm,
npm install --save icon-sdk-js
Then, import icon-sdk-js/build/icon-sdk-js.web.min.js module.
import IconService from 'icon-sdk-js/build/icon-sdk-js.web.min.js';

Using the SDK

Generate IconService

Generate IconService to communicate with the nodes.
The IconService class contains a set of API methods. It allows you to send transaction, check the result and get block information, etc. It accepts the HttpProvider which serves the purpose of connecting to HTTP and HTTPS based JSON-RPC servers. The HttpProvider takes the full URI where the server can be found. Here is a simple example how to initialize IconService class.
/* HttpProvider is used to communicate with http.
In this example, we use Yeouido node as provider. */
const provider = new HttpProvider('https://bicon.net.solidwallet.io/api/v3');
​
/* Create IconService instance */
const iconService = new IconService(provider);

Queries

All query methods of IconService returns a HttpCall instance. To execute the request and get the result value, you need to run execute() function of HttpCall instance. All requests will be executed asynchronously. Synchronous request is not available. For more information, check the API reference documentation.
const { CallBuilder } = IconService.IconBuilder;
​
/* Get block information by block height */
const block = await iconService.getBlockByHeight(1000).execute();
​
/* Get block information by block hash */
const block = await iconService.getBlockByHash('0xdb3···d95').execute();
​
/* Get latest block information */
const block = await iconService.getLastBlock().execute();
​
/* Returns the balance of a EOA address */
const balance = await iconService.getBalance('hx9d8···b57').execute();
​
/* Returns the SCORE API list */
const apiList = await iconService.getScoreApi('cx000···001').execute();
​
/* Returns the total number of issued ICX. */
const totalSupply = await iconService.getTotalSupply().execute();
​
/* Returns information about a transaction requested by transaction hash */
const txObj = await iconService.getTransaction('0xb90···238').execute();
​
/* Returns the result of a transaction by transaction hash */
const txObj = await iconService.getTransactionResult('0xb90···238').execute();
​
/* Generates a call instance using the CallBuilder */
const callObj = new CallBuilder()
.to('cxc24···6c7')
.method('balanceOf')
.params({ _owner: 'hx87a···d6a' })
.build()
​
/* Executes a call method to call a read-only API method on the SCORE immediately without creating a transaction on Loopchain */
const result = await iconService.call(callObj).execute();

Transactions

To invoke SCORE API for changing states, you need to send a transaction. Before sending a transaction, the transaction should be signed. It can be done using the Wallet object.
const { IconWallet } = IconService;
​
/* Creates an instance of Wallet. */
const wallet = IconWallet.create();
​
/* Load Wallet object by private key */
const wallet = IconWallet.loadPrivateKey('2ab···e4c');
​
/* Load Wallet object by keystore object */
const ks = { "version": 3 ··· "coinType": "icx" };
const pw = 'qwer1234!';
const wallet = IconWallet.loadKeystore(ks, pw);
Next, you need to build the transaction object using builder class.
/* Build `IcxTransaction` instance for sending ICX. */
const txObj = new IcxTransactionBuilder()
.from('hx462···bfd')
.to('hx87a···d6a')
.value(IconAmount.of(7, IconAmount.Unit.ICX).toLoop())
.stepLimit(IconConverter.toBigNumber(100000))
.nid(IconConverter.toBigNumber(3))
.nonce(IconConverter.toBigNumber(1))
.version(IconConverter.toBigNumber(3))
.timestamp((new Date()).getTime() * 1000)
.build()
​
/* Build `MessageTransaction` instance for sending data. */
const txObj = new MessageTransactionBuilder()
.from('hx462···bfd')
.to('hx87a···d6a')
.stepLimit(IconConverter.toBigNumber(100000))
.nid(IconConverter.toBigNumber(3))
.nonce(IconConverter.toBigNumber(1))
.version(IconConverter.toBigNumber(3))
.timestamp((new Date()).getTime() * 1000)
.data(IconConverter.fromUtf8('Hello'))
.build()
​
/* Build `DeployTransaction` instance for deploying SCORE. */
const txObj = new DeployTransactionBuilder()
.from('hx462···bfd')
.to('cx000···000')
.stepLimit(IconConverter.toBigNumber(2500000))
.nid(IconConverter.toBigNumber(3))
.nonce(IconConverter.toBigNumber(1))
.version(IconConverter.toBigNumber(3))
.timestamp((new Date()).getTime() * 1000)
.contentType('application/zip')
.content('0x504···000')
.params({
initialSupply: IconConverter.toHex('100000000000'),
decimals: IconConverter.toHex(18),
name: 'StandardToken',
symbol: 'ST',
})
.build()
​
/* Build `CallTransaction` instance for executing SCORE function. */
const txObj = new CallTransactionBuilder()
.from('hx902···3b5')
.to('cx350···48d')
.stepLimit(IconConverter.toBigNumber('2000000'))
.nid(IconConverter.toBigNumber('3'))
.nonce(IconConverter.toBigNumber('1'))
.version(IconConverter.toBigNumber('3'))
.timestamp((new Date()).getTime() * 1000)
.method('transfer')
.params({
_to: 'hxd00···497',
_value: IconConverter.toHex(IconAmount.of(1, IconAmount.Unit.ICX).toLoop()),
})
.build()
Using SignedTransaction object, you can make signature for transaction object. By passing SignedTransaction instance to IconService.sendTransaction() method, it will automatically generate transaction object including signature, and send to ICON node.
sendTransaction method returns a HttpCall instance. To execute the request and get the result value, you need to run execute() function of HttpCall instance. All requests will be executed asynchronously. Synchronous request is not available.
/* Create SignedTransaction instance */
const signedTransaction = new SignedTransaction(txObj, wallet)
​
/* Send transaction. It returns transaction hash. */
const txHash = await iconService.sendTransaction(signedTransaction).execute();

Code Examples

Install Dependency

Please go to quickstart directory and install dependency to use icon-sdk-js.
npm install // install dependencies for executing the quickstart project (including icon-sdk-js package)

Run example file

Run example file.
npm start // open http://localhost:3000/ in browser
If you want to rebuild icon-sdk-js library and run quickstart project, go to icon-sdk-js root directory and run npm run quickstart:rebuild command.
npm run quickstart:rebuild // open http://localhost:3000/ in browser

Set Node URL

If you want to use custom ICON node URL, change the value of NODE_URL variable in ./mockData/index.js. Default value of NODE_URL is https://bicon.net.solidwallet.io/api/v3
For more information on the testnet, see the documentation for the ICON network.
const NODE_URL = 'https://bicon.net.solidwallet.io/api/v3';

​

Wallet

This example shows how to create a new Wallet and load wallet with privateKey or Keystore file.
Create a wallet
Create new EOA by calling create function. After creation, the address and private Key can be looked up.
const wallet = IconWallet.create(); //Wallet Creation
console.log("Address: " + wallet.getAddress()); // Address Check
console.log("PrivateKey: " + wallet.getPrivateKey()); // PrivateKey Check
​
// Output
Address: hx4d37a7013c14bedeedbe131c72e97ab337aea159
PrivateKey: 00e1d6541bfd8be7d88be0d24516556a34ab477788022fa07b4a6c1d862c4de516
Load a wallet
You can call existing EOA by calling loadKeystore and loadPrivateKey function.
After creation, address and private Key can be looked up.
// Load Wallet with private key
const walletLoadedByPrivateKey = IconWallet.loadPrivateKey('38f792b95a5202ab431bfc799f7e1e5c74ec0b9ede5c6142ee7364f2c84d72f6');
console.log(walletLoadedByPrivateKey.getAddress());
// Output: hx902ecb51c109183ace539f247b4ea1347fbf23b5
console.log(walletLoadedByPrivateKey.getPrivateKey());
// Output: 38f792b95a5202ab431bfc799f7e1e5c74ec0b9ede5c6142ee7364f2c84d72f6);
​
// Get keystore object from wallet
const keystoreFile = walletLoadedByPrivateKey.store('qwer1234!');
// Load wallet with keystore file
const walletLoadedByKeyStore = IconWallet.loadKeystore(keystoreFile, 'qwer1234!');
console.log(walletLoadedByKeyStore.getAddress());
// Output: hx902ecb51c109183ace539f247b4ea1347fbf23b5
console.log(walletLoadedByKeyStore.getPrivateKey());
// Output: 38f792b95a5202ab431bfc799f7e1e5c74ec0b9ede5c6142ee7364f2c84d72f6);
Store the wallet
After Wallet object creation, Keystore file can be stored by calling store function.
After calling store, Keystore JSON object can be looked up with the returned value.
const privateKey = '38f792b95a5202ab431bfc799f7e1e5c74ec0b9ede5c6142ee7364f2c84d72f6'
const wallet = IconWallet.loadPrivateKey(privateKey);
console.log(wallet.store('qwer1234!'));
// Output:
// {
// "version": 3,
// "id": "e00e113c-1e45-47e4-b732-10f3d1903d75",
// "address": "hx7d3d4c743bb82b927ea8a0551a3b9288e722ac84",
// "crypto": {
// "ciphertext": "d5df37230528bbfc0015e93c61e60041a31fb63266f61ffec60a31f474d4d7d0",
// "cipherparams": {
// "iv": "feaf0cc19678e4b78369904a99ba411e"
// },
// "cipher": "aes-128-ctr",
// "kdf": "scrypt",
// "kdfparams": {
// "dklen": 32,
// "salt": "e2e3666919161044f7b369d6ad4296380d4a13b9b5e844301c64a502ea3da240",
// "n": 16384,
// "r": 8,
// "p": 1
// },
// "mac": "43789e78de4744d06c14cf966b9609fadbcd815b5380caf3f778797f9824d9d7"
// }
// }

ICX Transfer

This example shows how to transfer ICX and check the result.
For the Wallet and IconService creation, please refer to the information above.
ICX transfer transaction
In this example, you can create a Wallet with MockData.PRIVATE_KEY_1 and transfer 1 ICX to MockData.WALLET_ADDRESS_2.
const wallet = IconWallet.loadPrivateKey(MockData.PRIVATE_KEY_1);
const walletAddress = wallet.getAddress();
// 1 ICX -> 1000000000000000000 conversion
const value = IconAmount.of(1, IconAmount.Unit.ICX).toLoop();
console.log(value);
// Output: BigNumber {s: 1, e: 18, c: Array(1)}
You can get a step cost for transferring icx as follows.
async getDefaultStepCost() {
const { CallBuilder } = IconBuilder;
// Get governance score api list
const governanceApi = await this.iconService.getScoreApi(MockData.GOVERNANCE_ADDRESS).execute();
console.log(governanceApi)
const methodName = 'getStepCosts';
// Check input and output parameters of api if you need
const getStepCostsApi = governanceApi.getMethod(methodName);
const getStepCostsApiInputs = getStepCostsApi.inputs.length > 0 ? JSON.stringify(getStepCostsApi.inputs) : 'none';
const getStepCostsApiOutputs = getStepCostsApi.outputs.length > 0 ? JSON.stringify(getStepCostsApi.outputs) : 'none';
console.log(`[getStepCosts]\n inputs: ${getStepCostsApiInputs} \n outputs: ${getStepCostsApiOutputs}`);
​
// Get step costs by iconService.call
const callBuilder = new CallBuilder();
const call = callBuilder
.to(MockData.GOVERNANCE_ADDRESS)
.method(methodName)
.build();
const stepCosts = await this.iconService.call(call).execute();
return stepCosts.default
}
Generate transaction using the values above.
// networkId of node 1:mainnet, 2~:etc
const networkId = new BigNumber("3"); // input node’s networkld
const version = new BigNumber("3"); // version
​
// Recommended icx transfer step limit :
// use 'default' step cost in the response of getStepCosts API
const stepLimit = await this.getDefaultStepCost(); // Please refer to the above description.
​
// Timestamp is used to prevent the identical transactions. Only current time is required (Standard unit : us)
// If the timestamp is considerably different from the current time, the transaction will be rejected.
const timestamp = (new Date()).getTime() * 1000;
​
//Enter transaction information
const icxTransactionBuilder = new IcxTransactionBuilder();
const transaction = icxTransactionBuilder
.nid(networkId)
.from(walletAddress)
.to(MockData.WALLET_ADDRESS_2)
.value(value)
.version(version)
.stepLimit(stepLimit)
.timestamp(timestamp)
.build();
Generate SignedTransaction to add the signature of the transaction.
// Create signature of the transaction
const signedTransaction = new SignedTransaction(transaction, wallet);
// Read params to transfer to nodes
console.log(signedTransaction.getProperties());
// Output:
// {
// from: "hx902ecb51c109183ace539f247b4ea1347fbf23b5",
// nid: "0x3",
// nonce: "0x1",
// signature: "OE/yJbKn+3kXiC/5x1mvOCpdbTiCAvdlZDgSH31//alTe4kTEVRCETXsQx+Jkbfwa6Qel1PUddoowdkQJDLPrgE=",
// stepLimit: "0x186a0",
// timestamp: "0x578ed370a3780",
// to: "hxd008c05cbc0e689f04a5bb729a66b42377a9a497",
// value: "0xde0b6b3a7640000",
// version: "0x3",
// }
After calling sendTransaction from IconService, you can send a transaction and check the transaction’s hash value. ICX transfer is now sent.
// Send transaction
const txHash = await iconService.sendTransaction(signedTransaction).execute();
// Print transaction hash
console.log(txHash);
// Output
// 0x69c07ff23e2eafb068ec026f1a116082f0d869b3964531e43088f6638bcfe0f7
Check the transaction result
After the transaction is sent, the result can be looked up with the returned hash value.
In this example, you can check your transaction result every 2 seconds because of the block confirmation time. Checking the result is as follows:
// Check the result with the transaction hash
const transactionResult = await iconService.getTransactionResult(txHash).execute();
console.log("transaction status(1:success, 0:failure): "+transactionResult.status);
// Output
// transaction status(1:success, 0:failure): 1
You can check the following information using the TransactionResult.
  • status : 1 (success), 0 (failure)
  • to : transaction’s receiving address
  • failure : Only exists if status is 0(failure). code(str), message(str) property included
  • txHash : transaction hash
  • txIndex : transaction index in a block
  • blockHeight : Block height of the transaction
  • blockHash : Block hash of the transaction
  • cumulativeStepUsed : Accumulated amount of consumed step’s until the transaction is executed in block
  • stepUsed : Consumed step amount to send the transaction
  • stepPrice : Consumed step price to send the transaction
  • scoreAddress : SCORE address if the transaction generated SCORE (optional)
  • eventLogs : List of EventLogs written during the execution of the transaction.
  • logsBloom : Bloom Filter of the indexed data of the Eventlogs.
Check the ICX balance
In this example, you can check the ICX balance by looking up the transaction before and after the transaction.
ICX balance can be confirmed by calling getBalance function from IconService
// create or load wallet
const wallet = IconWallet.loadPrivateKey(MockData.PRIVATE_KEY_2);
// Check the wallet balance
const balance = await iconService.getBalance(wallet.getAddress()).execute();
console.log(balance);
​
// Output:
// 100432143214321432143

Token Deploy and Transfer

This example shows how to deploy IRC token and transfer deployed token.
For the Wallet and IconService generation, please refer to the information above.
Token deploy transaction
You need the SCORE Project to deploy token.
In this example, you will use ‘test.zi’ from the ‘resources’ folder.
*test.zi : SampleToken SCORE Project Zip file.
Generate a wallet using MockData.PRIVATE_KEY_1, then read the binary data from ‘test.zi’
const { Wallet } = this.iconService;
this.wallet = IconWallet.loadPrivateKey(MockData.PRIVATE_KEY_1);
​
this.content = '';
// Read test.zi from ‘resources’ folder.
Enter the basic information of the token you want to deploy.
const initialSupply = IconConverter.toBigNumber("100000000000");
const decimals = IconConverter.toBigNumber("18");
const tokenName = "StandardToken";
const tokenSymbol = "ST";
You can get the maximum step limit value as follows.
// Get apis that provides Governance SCORE
// GOVERNANCE_ADDRESS : cx0000000000000000000000000000000000000001
async getMaxStepLimit() {
const { CallBuilder } = IconBuilder;
​
const governanceApi = await this.iconService.getScoreApi(MockData.GOVERNANCE_ADDRESS).execute();
// "getMaxStepLimit" : the maximum step limit value that any SCORE execution should be bounded by.
const methodName = 'getMaxStepLimit';
// Check input and output parameters of api if you need
const getMaxStepLimitApi = governanceApi.getMethod(methodName);
​
const params = {};
params[getMaxStepLimitApi.inputs[0].name] = 'invoke';
​
// Get max step limit by iconService.call
const callBuilder = new CallBuilder();
const call = callBuilder
.to(MockData.GOVERNANCE_ADDRESS)
.method(methodName)
.params(params)
.build();
const maxStepLimit = await this.iconService.call(call).execute();
return IconConverter.toBigNumber(maxStepLimit)
}
Generate transaction with the given values above.
async buildDeployTransaction() {
const { DeployTransactionBuilder } = IconBuilder;
​
const initialSupply = IconConverter.toBigNumber("100000000000");
const decimals = IconConverter.toBigNumber("18");
const tokenName = "StandardToken";
const tokenSymbol = "ST";
const contentType = "application/zip";
// Enter token information
// key name ("initialSupply", "decimals", "name", "symbol")
// You must enter the given values. Otherwise, your transaction will be rejected.
const params = {
initialSupply: IconConverter.toHex(initialSupply),
decimals: IconConverter.toHex(decimals),
name: tokenName,
symbol: tokenSymbol
}
const installScore = MockData.SCORE_INSTALL_ADDRESS;
const stepLimit = await this.getMaxStepLimit();
const walletAddress = this.wallet.getAddress();
// networkId of node 1:mainnet, 2~:etc
const networkId = IconConverter.toBigNumber(3);
const version = IconConverter.toBigNumber(3);
// Timestamp is used to prevent the identical transactions. Only current time is required (Standard unit : us)
// If the timestamp is considerably different from the current time, the transaction will be rejected.
const timestamp = (new Date()).getTime() * 1000;
​
//Enter transaction information
const deployTransactionBuilder = new DeployTransactionBuilder();
const transaction = deployTransactionBuilder
.nid(networkId)
.from(walletAddress)
.to(installScore)
.stepLimit(stepLimit)
.timestamp(timestamp)
.contentType(contentType)
.content(`0x${this.content}`)
.params(params)
.version(version)
.build();
return transaction;
}
Generate SignedTransaction to add signature to the transaction.
// Create signature of the transaction
const signedTransaction = new SignedTransaction(transaction, this.wallet);
// Read params to transfer to nodes
const signedTransactionProperties = JSON.stringify(signedTransaction.getProperties()).split(",").join(", \n");
You can check the transaction hash value by calling sendTransaction from ‘IconService`. Deployment is now completed.
this.deployTxHash = await this.iconService.sendTransaction(signedTransaction).execute();
Check the deploy transaction result
After the transaction is sent, the result can be looked up with the returned hash value. You can also check the ST Token score address that you deployed.
Checking the result is as follows:
// Check the result with the transaction hash
const transactionResult = await iconService.getTransactionResult(this.deployTxHash).execute();
​
console.log("transaction status(1:success, 0:failure): "+transactionResult.status);
console.log("Your score address: " + transactionResult.scoreAddress);
​
// Output
// transaction status(1:success, 0:failure): 1
// Your score address: cx19584dcfacd0d7cc5e0562a53959069213d7adca
For the 'TransactionResult', please refer to the IcxTransactionExample.
Token transfer transaction
You can send the ST token that you deployed right before.
You can generate Wallet using MockData.PRIVATE_KEY_1 just like in the case of IcxTransactionExample, then send 1 ST Token to MockData.WALLET_ADDRESS_2
You need the token address to send your token.
const wallet = IconWallet.loadPrivateKey(MockData.PRIVATE_KEY_1);
const toAddress = MockData.WALLET_ADDRESS_2;
const tokenAddress = this.scoreAddress; //ST Token Address that you deployed
const tokenDecimals = 18; // token decimal
// 1 ICX -> 1000000000000000000 conversion
const value = IconAmount.of(1, IconAmount.Unit.ICX).toLoop();
You can get a step cost to send token as follows.
async getDefaultStepCost() {
const { CallBuilder } = IconBuilder;
​
// Get apis that provides Governance SCORE
// GOVERNANCE_ADDRESS : cx0000000000000000000000000000000000000001
const governanceApi = await this.iconService.getScoreApi(MockData.GOVERNANCE_ADDRESS).execute();
console.log(governanceApi)
const methodName = 'getStepCosts';
​
// Get step costs by iconService.call
const callBuilder = new CallBuilder();
const call = callBuilder
.to(MockData.GOVERNANCE_ADDRESS)
.method(methodName)
.build();
const stepCosts = await this.iconService.call(call).execute();
// For sending token, it is about twice the default value.
return IconConverter.toBigNumber(stepCosts.default).times(2)
}
Generate Transaction with the given parameters above. You have to add receiving address and value to param object to send token.
async buildTokenTransaction() {
const { CallTransactionBuilder } = IconBuilder;
​
const walletAddress = this.wallet.getAddress();
// You can use "governance score apis" to get step costs.
const value = IconAmount.of(1, IconAmount.Unit.ICX).toLoop();
const stepLimit = await this.getDefaultStepCost();
// networkId of node 1:mainnet, 2~:etc
const networkId = IconConverter.toBigNumber(3);
const version = IconConverter.toBigNumber(3);
// Timestamp is used to prevent the identical transactions. Only current time is required (Standard unit : us)
// If the timestamp is considerably different from the current time, the transaction will be rejected.
const timestamp = (new Date()).getTime() * 1000;
// SCORE name that send transaction is “transfer”.
const methodName = "transfer";
// Enter receiving address and the token value.
// You must enter the given key name("_to", "_value"). Otherwise, the transaction will be rejected.
const params = {
_to: MockData.WALLET_ADDRESS_2,
_value: IconConverter.toHex(value)
}
​
//Enter transaction information
const tokenTransactionBuilder = new CallTransactionBuilder();
const transaction = tokenTransactionBuilder
.nid(networkId)
.from(walletAddress)
.to(this.scoreAddress)
.stepLimit(stepLimit)
.timestamp(timestamp)
.method(methodName)
.params(params)
.version(version)
.build();
return transaction;
}
Generate SignedTransaction to add signature to your transaction.
// Generate transaction signature.
const signedTokenTransfer = new SignedTransaction(transaction, wallet);
// Read params to send to nodes.
console.log(signedTokenTransfer.getProperties());
Call sendTransaction from ‘IconService’ to check the transaction hash. Token transaction is now sent.
// Send transaction
this.transactionTxHash = await iconService.sendTransaction(signedTokenTransfer).execute();
// Print transaction hash
console.log(this.transactionTxHash);
// Output
// 0x6b17886de346655d96373f2e0de494cb8d7f36ce9086cb15a57d3dcf24523c8f
Check the transfer transaction result
You can check the result with the returned hash value of your transaction.
In this example, you can check your transaction result in every 2 seconds because of the block confirmation time. Checking the result is as follows:
// Check the result with the transaction hash
const transactionResult = await iconService.getTransactionResult(this.transactionTxHash).execute();
console.log("transaction status(1:success, 0:failure): "+transactionResult.status);
// Output
// transaction status(1:success, 0:failure):1
For the TransactionResult, please refer to the IcxTransactionExample.

Check the token balance

In this example, you can check the token balance before and after the transaction.
You can check the token balance by calling ‘balanceOf’ from the token SCORE.
const { CallBuilder } = IconBuilder;
const tokenAddress = this.scoreAddress;
// Method name to check the balance
const methodName = "balanceOf";
// You must enter the given key name (“_owner”).
const params = {
_owner: address
}
const callBuilder = new CallBuilder();
const call = callBuilder
.to(tokenAddress)
.method(methodName)
.params(params)
.build();
// Check the wallet balance
const balance = await this.iconService.call(call).execute();

Sync Block

This example shows how to read block information and print the transaction result for every block creation.
Please refer to above for Wallet and IconService creation.
Read the block information
In this example, 'getLastBlock' is called periodically in order to check the new blocks,
by updating the transaction information for every block creation.
// Check the recent blocks
const block = await iconService.getLastBlock().execute();
console.log(block.height);
// Output
// 237845
If a new block has been created, get the transaction list.
const txList = block.getTransactions();
You can check the following information using the ConfirmedTransaction:
  • version : json rpc server version
  • to : Receiving address of transaction
  • value: The amount of ICX coins to transfer to the address. If omitted, the value is assumed to be 0
  • timestamp: timestamp of the transmitting transaction (unit: microseconds)
  • nid : network ID
  • signature: digital signature data of the transaction
  • txHash : transaction hash
  • dataType: A value indicating the type of the data item (call, deploy, message)
  • data: Various types of data are included according to dataType.
Transaction output
async syncBlock(block) {
// the transaction list of blocks
console.log(block)
const txList = block.getTransactions();
​
Promise.all(
txList.map(async transaction => {
const txResult = await this.iconService.getTransactionResult(transaction.txHash).execute();
​
// Print icx transaction
if ((transaction.value !== undefined) && transaction.value > 0) {
document.getElementById("S03-2").innerHTML += `<li>${block.height} - [ICX] status: ${txResult.status === 1 ? 'success' : 'failure'} | amount: ${transaction.value}</li>`
}
​
// Print token transaction
if (transaction.dataType !== undefined &&
transaction.dataType === "call") {
const method = transaction.data.method;
​
if (method !== null && method === "transfer") {
const params = transaction.data.params;
const value = IconConverter.toBigNumber(params["_value"]); // value
const toAddr = params["_to"];
​
const tokenName = await this.getTokenName(transaction.to);
const symbol = await this.getTokenSymbol(transaction.to);
​
document.getElementById("S03-2").innerHTML += `<li>${block.height} - [${tokenName} - ${symbol}] status: ${txResult.status === 1 ? 'success' : 'failure'} | amount: ${value}</li>`;
}
}
})
)
​
this.prevHeight = block.height;
}
Check the token name & symbol
You can check the token SCORE by calling the name and symbol functions.
async getTokenName(to) {
const { CallBuilder }