Sending ERC20 tokens

sender.js

// https://github.com/ethereum/wiki/wiki/JavaScript-API
// npm install --save web3@0.20.7 ethereumjs-tx bignumber.js

const Web3 = require("web3");
const Tx = require("ethereumjs-tx");
const BigNumber = require("bignumber.js");

const erc20_ABI = 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// Contract settings
const web3 = new Web3(new Web3.providers.HttpProvider("https://rinkeby.infura.io/<projectid>"));
const contractAddress = "0xYOUR_CONTRACT_ADDRESS";
const contract = web3.eth.contract(erc20_ABI).at(address);
const decimals = 2; // DECIMALS

// From
const sender = "0xSENDER";
const privateKey = Buffer.from("PRIVATE_KEY", 'hex');

// To
const recipient = "0xRECIPIENT";
const amount = new BigNumber("1.99"); // amount of tokens

// Calculation estimated gas
const callData = contract.transfer.getData(recipient, amount.shiftedBy(decimals).toString());
const gasPrice = web3.eth.gasPrice;
const gasPriceHex = web3.toHex(gasPrice);
const gasEstimate = web3.eth.estimateGas({
    from: sender,
    to: contractAddress,
    data: callData
});
let gasLimitHex = web3.toHex(Math.ceil(gasEstimate*1.5)); // multiply it by 1.5

// Transaction
const nonce = web3.eth.getTransactionCount(sender);
const nonceHex = web3.toHex(nonce);

const rawTx = {
    nonce: nonceHex,
    gasPrice: gasPriceHex,
    gasLimit: gasLimitHex,
    from: sender,
    to: contractAddress,
    data: callData
};

let tx = new Tx(rawTx);
tx.sign(privateKey);

const serializedTx = tx.serialize();

web3.eth.sendRawTransaction("0x" + serializedTx.toString("hex"), function(err, hash) {
    if (!!err)
        console.error("Error while sending transaction:", err);
    else
        console.log("Done, transaction id =", hash);
});