67 DEX

In this project, I created my own Token, DEXLiquidity Pool.

Warning: This code is not audited. Use at your own risk.\

A decentralized exchange (DEX) smart contract built on Ethereum using Solidity.

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Overview

This DEX allows users to:

• Swap ETH ↔ Tokens — Trade ETH for tokens and vice versa
• Add Liquidity — Provide ETH + tokens to the pool and earn LP tokens
• Remove Liquidity — Burn LP tokens to withdraw your share of the pool

How It Works

The DEX uses an Automated Market Maker (AMM) with the constant product formula:

x × y = k

x = ETH reserve
y = Token reserve
k = constant (stays the same)

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Contract Functions

Function	Description
addLiquidity()	Add ETH + tokens to the pool, receive LP tokens
removeLiquidity()	Burn LP tokens, receive ETH + tokens back
swapEthToToken()	Swap ETH for tokens
swapTokenToEth()	Swap tokens for ETH
getAmountOfTokens()	Calculate output amount for a swap
getTokensInContract()	Get token balance in the pool

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Getting Started

Prerequisites

• Node.js (v16+)
• Yarn or npm

Installation

# Install dependencies
yarn install
# or
npm install

Build

Compile the contract:

npx thirdweb build

Deploy

Deploy the contract to any EVM chain:

npx thirdweb deploy

This will open a browser where you can select the network and configure deployment.

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Full Tutorial: Create Token → Deploy DEX → Add Liquidity

Step 1: Create Your Token on Thirdweb

1. Go to thirdweb.com/explore
2. Search for "Token" or "TokenERC20"
3. Click Deploy Now
4. Fill in the details:
   • Name: Your token name (e.g., "67")
   • Symbol: Token symbol (e.g., "67")
   • Admin: Your wallet address
5. Select your network (e.g., Ethereum, zkSync)
6. Click Deploy and confirm in MetaMask
7. Save your token contract address! (e.g., 0x1234...abcd)

Step 2: Mint Tokens to Your Wallet

1. Go to your token contract on thirdweb dashboard
2. Click "Tokens" in the sidebar
3. Click "+ Mint"
4. Enter the amount (e.g., 1000000 for 1 million tokens)
5. Click Mint and confirm in MetaMask
6. You now have tokens in your wallet!

Step 3: Deploy the DEX Contract

1. In your project folder, run:

npx thirdweb build
npx thirdweb deploy

2. A browser window opens. Fill in the constructor parameters:

   • _token: Your token contract address from Step 1 (e.g., 0x1234...abcd)
   • _defaultAdmin: Your wallet address
   • _name: LP token name (e.g., "67 DEX LP")
   • _symbol: LP token symbol (e.g., "67LP")

3. Select your network (same as your token!)

4. Click Deploy and confirm in MetaMask

5. Save your DEX contract address! (e.g., 0xDEX...5678)

Step 4: Approve DEX to Spend Your Tokens

Before adding liquidity, you must allow the DEX to transfer your tokens.

1. Go to your TOKEN contract on thirdweb dashboard
2. Click "Write" tab
3. Find approve function
4. Enter:
   • spender: Your DEX contract address (from Step 3)
   • amount: 1000000000000000000000000 (1 million tokens with 18 decimals)
5. Click Execute and confirm in MetaMask

Step 5: Add Liquidity to the DEX

Now add your tokens + ETH to create the liquidity pool.

1. Go to your DEX contract on thirdweb dashboard
2. Click "Write" tab
3. Find addLiquidity function
4. Enter:
   • Amount: Number of tokens (with 18 decimals)
     • Example: 100000000000000000000000 = 100,000 tokens
   • Native Token Value: ETH to add
     • Example: 0.1 = 0.1 ETH
5. Click Execute and confirm in MetaMask

Step 6: Verify It Worked

1. Go to your DEX contract → "Read" tab
2. Call balanceOf with your wallet address
   • Should show your LP tokens (not 0!)
3. Call getTokensInContract
   • Should show tokens in the pool
4. Check the contract's ETH balance on block explorer

Summary

Step 1: Create token on thirdweb           → Get TOKEN_ADDRESS
Step 2: Mint tokens to your wallet         → You have tokens
Step 3: Deploy DEX with npx thirdweb deploy → Get DEX_ADDRESS
Step 4: Approve DEX to spend tokens        → TOKEN.approve(DEX_ADDRESS, amount)
Step 5: Add liquidity                      → DEX.addLiquidity(tokens) + send ETH
Step 6: Verify LP balance > 0              → Success!

Common Mistakes

Problem	Solution
LP balance is 0	You didn't send ETH (Native Token Value was 0)
Transaction failed	You didn't approve the DEX first
Wrong network	Make sure token and DEX are on the same network
Not enough gas	Get more ETH for gas fees

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Project Structure

dexcontract/
├── contracts/
│   └── Contract.sol    # Main DEX contract
├── scripts/
│   └── verify/         # Verification scripts
├── hardhat.config.js   # Hardhat configuration
└── package.json

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Key Concepts

LP Tokens

When you add liquidity, you receive LP (Liquidity Provider) tokens. These represent your share of the pool.

Slippage

Larger trades have more price impact. The AMM formula ensures prices adjust based on supply and demand.

Reserves

The pool holds both ETH and tokens. The ratio between them determines the price.

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