This is a fullstack DApp NFT Marketplace built as a study project to learn more about blockchain and smart contract development.
Made with NodeJS, Hardhat, Solidity, ReactJS, NextJS and Vercel.

Checkout the live demo: https://nft-marketplace-markkop.vercel.app/

You can create (mint) new tokens, uploading their image and metadata on IPFS using Pinata.
If you've created or bought an NFT, you may also sell it by setting a price and paying a listing fee.
When buying an NFT, the price will be transferred to the seller and the listing fee to the NFT Marketplace owner.
It's also possible to cancel a market item, transferring it back to the owner.

There are only two pages to view market's NFTs:

• Market Page

Shows all NFTs that are available to be bought.
This page will show NFTs even if the user doesn't have the Metamask extension or isn't connected to the dapp.

NFTs available

• My NFTs Page

Show all account's created, owned and on sale NFTs.
Here you keep track of NFT's you've created and check for how much they've been last sold and their current owner.
You can also list your current owned NFTs or cancel existing ones.
To view this page, you must have Metamask installed and have it connected to Polygon's Testnet network.

Created and owned NFTs

If the Metamask extension is not detected on "My NFTs" page, a message with a download button will be prompted to the user.

Download metamask message and buttons

If the user has the extension, but is not connected, a message and a connect button will be shown.

Connect wallet message and button

If the Polygon's Testnet network is not detected, a message and an ADD/CHANGE network button will be available.

Add/Change Network message and button

If the connected account is low on balance of Matic tokens, a message with a faucet link is provided.

A low on balance message with a faucet link

When changing account or network, the page will refresh updating only the affected components.

Components update on account change

When performing an action, a loading feedback is shown and the card updates to its new state automatically.

Buying an NFT and its feedbacks

Frontend is automatically deployed using Vercel's Github integration, but contracts have to be manually deployed to keep a better control on them.
However, new deployed contract addresses can be updated on the frontend simply by running a script that modifies Vercel's project environment variables and triggers a new frontend deployment.

• Copy .env.local.example to .env.local and fill it with environment variables
• Run npm run node to start a local EVM blockchain testnet
• Run npm run setup to deploy NFT and Marketplace contracts and perform some initial actions to the local blockchain
• Run npm run dev to start frontend application
• Make sure to use Localhost 8545 as the Metamask's network
• Make sure to import local Account #0 and #1 into Metamask accounts.

• Frontend is deployed automatically on main branch using Vercel's github integration
• Set ACCOUNT_PRIVATE_KEY in .env.local and send it some Polygon's Testnet Matic tokens
• Run npm run deploy:mumbai to deploy contracts to Polygon`s Testnet (Mumbai)
• Optional: do the same for ACCOUNT2_PRIVATE_KEY env and run npm run setup-marketplace:mumbai to setup the marketplace with existing tokens and sales.
• Run npm run env to update Vercel's environment variables with the new deployed contract addresses.*
• Make sure to use Polygon Testnet Mumbai as Metamask's network

* You'll need to create the envs on Vercel first

• Updating NFT UI Cards after an action was performed
• Dealing with Metamask's accountsChanged event being fired twice on mobile
• Building a Web3 context provider
• Debugging different problems that ended up causing "Estimate gas failed" errors*

* They're usually caused by incorrect contract addresses and wrong default gas values

• Refactor frontend code to accept other networks besides Mumbai
• Lazyload for NFTs images and metadata
• Add support for custom ERC20 tokens as payment (started on #2)

Try changing hardhat.config.js mumbai gas values.
I'm using the ones I've found here:
https://forum.moralis.io/t/deploy-to-polygon-matic-mumbai-fails/700

Reset your Metamask account transaction history.
Find out more on:
https://medium.com/@thelasthash/solved-nonce-too-high-error-with-metamask-and-hardhat-adc66f092cd

• FreeCodeCamp’s Solidity, Blockchain, and Smart Contract Course
• Building a Full Stack NFT Marketplace on Ethereum with Polygon
• Chainlist.org source code
• Import & Test a Popular NFT Smart Contract with Hardhat & Ethers