Merge pull request #17 from MrBlockchain22/patch-4

Add USDC on XDC QuickStart Guide to Developers Section

Author: AnilChinchawale

docs/xdcchain/developers/USDC QuickStart Guide

@@ -0,0 +1,209 @@
+---
+title: USDC on XDC QuickStart Guide
+---
+
+# USDC on XDC QuickStart Guide
+
+## Overview
+
+USDC is a digital dollar issued by Circle, also known as a stablecoin, and is available on many of the world’s leading blockchains. Designed to represent US dollars on the internet, USDC is backed 100% by highly liquid cash and cash-equivalent assets, making it redeemable 1:1 for USD.
+
+On the XDC Network, USDC behaves like any standard ERC-20 token — enabling fast, secure, and programmable digital dollar transactions.
+
+This guide walks you through building a standalone `index.js` script using **Viem** and **Node.js** to check your USDC balance and send a test transfer to another address on the **XDC Apothem Testnet**.
+
+---
+
+## Prerequisites
+
+- Node.js v18+ with `"type": "module"` in `package.json`
+- `viem` and `dotenv` packages installed
+- An XDC Apothem testnet wallet funded with testnet USDC and XDC (for gas fees)
+- A `.env` file with:
+  - `PRIVATE_KEY`
+  - `RECIPIENT_ADDRESS`
+
+> To get testnet USDC, use Circle’s CCTP v2 Sample App to transfer USDC cross-chain to your XDC wallet.
+
+---
+
+## Project Setup
+
+### 1. Initialize Project & Install Dependencies
+
+```bash
+npm init -y
+npm install viem dotenv
+````
+
+### 2. Create Environment File
+
+In your project root, create a `.env` file and add:
+
+```env
+PRIVATE_KEY=<YOUR_PRIVATE_KEY>         # Must be 0x-prefixed 64-character hex
+RECIPIENT_ADDRESS=0x<RECIPIENT_ADDRESS>
+```
+
+### 3. Create Your Script File
+
+In the same directory, create a file named `index.js`.
+
+Ensure `"type": "module"` is set in your `package.json`.
+
+---
+
+## Script Breakdown
+
+### 1. Import Modules & Define USDC Constants
+
+```js
+import 'dotenv/config';
+import { createPublicClient, createWalletClient, http, formatUnits, parseUnits } from 'viem';
+import { privateKeyToAccount } from 'viem/accounts';
+import { xdcTestnet } from 'viem/chains';
+
+const USDC_ADDRESS = '0xb5AB69F7bBada22B28e79C8FFAECe55eF1c771D4';
+const USDC_DECIMALS = 6;
+const USDC_ABI = [
+  {
+    name: 'balanceOf',
+    type: 'function',
+    stateMutability: 'view',
+    inputs: [{ name: 'account', type: 'address' }],
+    outputs: [{ name: '', type: 'uint256' }],
+  },
+  {
+    name: 'transfer',
+    type: 'function',
+    stateMutability: 'nonpayable',
+    inputs: [
+      { name: 'to', type: 'address' },
+      { name: 'amount', type: 'uint256' },
+    ],
+    outputs: [{ name: '', type: 'bool' }],
+  },
+];
+```
+
+---
+
+### 2. Load & Validate Environment Variables
+
+```js
+const PRIVATE_KEY_RAW = process.env.PRIVATE_KEY;
+const RECIPIENT = process.env.RECIPIENT_ADDRESS || process.env.RECIPIENT;
+
+if (!PRIVATE_KEY_RAW) {
+  console.error('Error: Set PRIVATE_KEY in your .env file');
+  process.exit(1);
+}
+if (!RECIPIENT) {
+  console.error('Error: Set RECIPIENT_ADDRESS or RECIPIENT in your .env file');
+  process.exit(1);
+}
+if (!/^0x[a-fA-F0-9]{40}$/.test(RECIPIENT)) {
+  console.error('Error: Recipient address is not a valid Ethereum address');
+  process.exit(1);
+}
+
+const PRIVATE_KEY = PRIVATE_KEY_RAW.startsWith('0x') ? PRIVATE_KEY_RAW : '0x' + PRIVATE_KEY_RAW;
+```
+
+---
+
+### 3. Initialize Viem Clients
+
+```js
+const account = privateKeyToAccount(PRIVATE_KEY);
+const publicClient = createPublicClient({ chain: xdcTestnet, transport: http() });
+const walletClient = createWalletClient({ account, chain: xdcTestnet, transport: http() });
+```
+
+---
+
+### 4. Main Transfer Logic
+
+```js
+(async () => {
+  try {
+    const balance = await publicClient.readContract({
+      address: USDC_ADDRESS,
+      abi: USDC_ABI,
+      functionName: 'balanceOf',
+      args: [account.address],
+    });
+
+    const balanceFormatted = Number(formatUnits(balance, USDC_DECIMALS));
+    const amount = 10;
+
+    console.log('Sender:', account.address);
+    console.log('Recipient:', RECIPIENT);
+    console.log('USDC balance:', balanceFormatted);
+
+    if (amount > balanceFormatted) {
+      console.error('Error: Insufficient USDC balance');
+      process.exit(1);
+    }
+
+    const amountInDecimals = parseUnits(amount.toString(), USDC_DECIMALS);
+
+    const hash = await walletClient.writeContract({
+      address: USDC_ADDRESS,
+      abi: USDC_ABI,
+      functionName: 'transfer',
+      args: [RECIPIENT, amountInDecimals],
+    });
+
+    console.log('Transfer successful!');
+    console.log('Tx hash:', hash);
+    console.log('Explorer:', `https://testnet.xdcscan.com/tx/${hash}`);
+  } catch (err) {
+    console.error('Transfer failed:', err.message || err);
+    process.exit(1);
+  }
+
+  process.exit(0);
+})();
+```
+
+---
+
+## Run the Script
+
+Use the following command:
+
+```bash
+node index.js
+```
+
+If successful, you’ll see output like:
+
+```
+Sender: 0x1A2b...7890
+Recipient: 0x9F8f...1234
+USDC balance: 250.0
+Transfer successful!
+Tx hash: 0xabc123...def456
+Explorer: https://testnet.xdcscan.com/tx/0xabc123...def456
+```
+
+---
+
+## Important Notes
+
+* **Testnet Only**: USDC on Apothem has no real value.
+* **Security**: Never commit your `.env` file. Treat private keys as sensitive.
+* **Gas Fees**: Get free XDC from the [XDC Faucet](https://faucet.apothem.network/).
+* **Lightweight ABI**: Only the necessary functions (`balanceOf`, `transfer`) are used.
+* **Viem Behavior**: Viem auto-handles RPC interaction, account signing, and encoding/decoding.
+
+---
+
+## Learn More
+
+Explore the full Circle USDC integration guide in the [Circle Developer Docs](https://developers.circle.com/docs/usdc).
+
+```
+
+---