How to send ERC20 token with Web3 and JavaScript
2 min readDec 19, 2018
const fs = require(‘fs’);const path = require(‘path’);const Web3API = require(‘web3’);const axios = require(‘axios’);/*** Fetch the current transaction gas prices from https://ethgasstation.info/** @return {object} Gas prices at different priorities*/const getCurrentGasPrices = async () => {let response = await axios.get(‘https://ethgasstation.info/json/ethgasAPI.json');let prices = {low: response.data.safeLow / 10,medium: response.data.average / 10,high: response.data.fast / 10};console.log(“\r\n”);console.log(`Current ETH Gas Prices (in GWEI):`);console.log(“\r\n”);console.log(`Low: ${prices.low} (transaction completes in < 30 minutes)`);console.log(`Standard: ${prices.medium} (transaction completes in < 5 minutes)`);console.log(`Fast: ${prices.high} (transaction completes in < 2 minutes)`);console.log(“\r\n”);return prices};const main = async () => {const web3 = new Web3API(new Web3API.providers.HttpProvider(‘https://mainnet.infura.io'));const privateKey = “0x….”;const tokenAddress = “0x….”;const fromAddress = “0x….”;const toAddress = “0x….”;// ABI to transfer ERC20 Tokenlet abi = JSON.parse(fs.readFileSync(path.join(__dirname, ‘.’, ‘main_contract.json’), ‘utf-8’));// calculate ERC20 token amountlet amount = 1;let tokenAmount = web3.utils.toWei(amount.toString(), ‘ether’)// Get ERC20 Token contract instancelet contract = new web3.eth.Contract(abi, tokenAddress, {from: fromAddress});// How many tokens do I have before sending?let balance = await contract.methods.balanceOf(fromAddress).call();console.log(`Balance before send: ${balance}`);// EIP 155 — List of Chain ID’s:const chainList = {mainnet: 1,morden: 2,ropsten: 3,rinkeby: 4,ubiqMainnet: 8,ubiqTestnet: 9,rootstockMainnet: 30,rootstockTestnet: 31,kovan: 42,ethereumClassicMainnet: 61,ethereumClassicTestnet: 62,ewasmTestnet: 66,gethPrivateChains: 1337};// The gas price is determined by the last few blocks median gas price.const avgGasPrice = await web3.eth.getGasPrice();// current transaction gas prices from https://ethgasstation.info/const currentGasPrices = await getCurrentGasPrices();/*** With every new transaction you send using a specific wallet address,* you need to increase a nonce which is tied to the sender wallet.*/let nonce = web3.eth.getTransactionCount(fromAddress);// Will call estimate the gas a method execution will take when executed in the EVM without.let estimateGas = await web3.eth.estimateGas({“value”: ‘0x0’, // Only tokens“data”: contract.methods.transfer(toAddress, tokenAmount).encodeABI(),“from”: fromAddress,“to”: toAddress});console.log({estimateGas: estimateGas});// Build a new transaction object.const transaction = {“value”: ‘0x0’, // Only tokens“data”: contract.methods.transfer(toAddress, tokenAmount).encodeABI(),“from”: fromAddress,“to”: toAddress,“gas”: web3.utils.toHex(estimateGas * 1.10),“gasLimit”: web3.utils.toHex(estimateGas * 1.10),“gasPrice”: web3.utils.toHex(Math.trunc(currentGasPrices.medium * 1e9)),“chainId”: web3.utils.toHex(chainList.mainnet)};// Creates an account object from a private key.const senderAccount = web3.eth.accounts.privateKeyToAccount(privateKey);/*** This is where the transaction is authorized on your behalf.* The private key is what unlocks your wallet.*/const signedTransaction = await senderAccount.signTransaction(transaction);console.log({transaction: transaction,amount: amount,tokenAmount: tokenAmount,avgGasPrice: avgGasPrice,signedTransaction: signedTransaction});// We’re ready! Submit the raw transaction details to the provider configured above.try {const receipt = await web3.eth.sendSignedTransaction(signedTransaction.rawTransaction);console.log({receipt: receipt});} catch (error) {console.log({error: error.message});}};main();
