index.js

function start() {
  document.getElementById("myDIV").style.display = "none" ;
}

if (window.ethereum) {
  window.web3 = new Web3(window.ethereum)
  try {
      // ask user for permission
      ethereum.enable()
      // user approved permission
  } catch (error) {
      // user rejected permission
      console.log('user rejected permission')
  }
}
else if (window.web3) {
  window.web3 = new Web3(window.web3.currentProvider)
  // no need to ask for permission
}
else {
  window.alert('Non-Ethereum browser detected. You should consider trying MetaMask!')
}
console.log (window.web3.currentProvider)


// contractAddress and abi are setted after contract deploy
var contractAddress = '0x2f9B0A57C01fb9bd3CF29D4D0e16F5f71aCEDb18';
var abi = [
	{
		"inputs": [],
		"stateMutability": "nonpayable",
		"type": "constructor"
	},
	{
		"anonymous": false,
		"inputs": [
			{
				"indexed": true,
				"internalType": "address",
				"name": "owner",
				"type": "address"
			},
			{
				"indexed": true,
				"internalType": "address",
				"name": "approved",
				"type": "address"
			},
			{
				"indexed": true,
				"internalType": "uint256",
				"name": "tokenId",
				"type": "uint256"
			}
		],
		"name": "Approval",
		"type": "event"
	},
	{
		"anonymous": false,
		"inputs": [
			{
				"indexed": true,
				"internalType": "address",
				"name": "owner",
				"type": "address"
			},
			{
				"indexed": true,
				"internalType": "address",
				"name": "operator",
				"type": "address"
			},
			{
				"indexed": false,
				"internalType": "bool",
				"name": "approved",
				"type": "bool"
			}
		],
		"name": "ApprovalForAll",
		"type": "event"
	},
	{
		"inputs": [
			{
				"internalType": "address",
				"name": "to",
				"type": "address"
			},
			{
				"internalType": "uint256",
				"name": "tokenId",
				"type": "uint256"
			}
		],
		"name": "approve",
		"outputs": [],
		"stateMutability": "nonpayable",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "uint256",
				"name": "_tokennumber",
				"type": "uint256"
			}
		],
		"name": "mint",
		"outputs": [],
		"stateMutability": "payable",
		"type": "function"
	},
	{
		"inputs": [],
		"name": "process",
		"outputs": [],
		"stateMutability": "nonpayable",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "address",
				"name": "from",
				"type": "address"
			},
			{
				"internalType": "address",
				"name": "to",
				"type": "address"
			},
			{
				"internalType": "uint256",
				"name": "tokenId",
				"type": "uint256"
			}
		],
		"name": "safeTransferFrom",
		"outputs": [],
		"stateMutability": "nonpayable",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "address",
				"name": "from",
				"type": "address"
			},
			{
				"internalType": "address",
				"name": "to",
				"type": "address"
			},
			{
				"internalType": "uint256",
				"name": "tokenId",
				"type": "uint256"
			},
			{
				"internalType": "bytes",
				"name": "_data",
				"type": "bytes"
			}
		],
		"name": "safeTransferFrom",
		"outputs": [],
		"stateMutability": "nonpayable",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "address",
				"name": "operator",
				"type": "address"
			},
			{
				"internalType": "bool",
				"name": "approved",
				"type": "bool"
			}
		],
		"name": "setApprovalForAll",
		"outputs": [],
		"stateMutability": "nonpayable",
		"type": "function"
	},
	{
		"anonymous": false,
		"inputs": [
			{
				"indexed": true,
				"internalType": "address",
				"name": "from",
				"type": "address"
			},
			{
				"indexed": true,
				"internalType": "address",
				"name": "to",
				"type": "address"
			},
			{
				"indexed": true,
				"internalType": "uint256",
				"name": "tokenId",
				"type": "uint256"
			}
		],
		"name": "Transfer",
		"type": "event"
	},
	{
		"inputs": [
			{
				"internalType": "address",
				"name": "from",
				"type": "address"
			},
			{
				"internalType": "address",
				"name": "to",
				"type": "address"
			},
			{
				"internalType": "uint256",
				"name": "tokenId",
				"type": "uint256"
			}
		],
		"name": "transferFrom",
		"outputs": [],
		"stateMutability": "nonpayable",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "address",
				"name": "owner",
				"type": "address"
			}
		],
		"name": "balanceOf",
		"outputs": [
			{
				"internalType": "uint256",
				"name": "",
				"type": "uint256"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [],
		"name": "baseURI",
		"outputs": [
			{
				"internalType": "string",
				"name": "",
				"type": "string"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "uint256",
				"name": "tokenId",
				"type": "uint256"
			}
		],
		"name": "getApproved",
		"outputs": [
			{
				"internalType": "address",
				"name": "",
				"type": "address"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "address",
				"name": "owner",
				"type": "address"
			},
			{
				"internalType": "address",
				"name": "operator",
				"type": "address"
			}
		],
		"name": "isApprovedForAll",
		"outputs": [
			{
				"internalType": "bool",
				"name": "",
				"type": "bool"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [],
		"name": "name",
		"outputs": [
			{
				"internalType": "string",
				"name": "",
				"type": "string"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "uint256",
				"name": "tokenId",
				"type": "uint256"
			}
		],
		"name": "ownerOf",
		"outputs": [
			{
				"internalType": "address",
				"name": "",
				"type": "address"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "bytes4",
				"name": "interfaceId",
				"type": "bytes4"
			}
		],
		"name": "supportsInterface",
		"outputs": [
			{
				"internalType": "bool",
				"name": "",
				"type": "bool"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [],
		"name": "symbol",
		"outputs": [
			{
				"internalType": "string",
				"name": "",
				"type": "string"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "uint256",
				"name": "index",
				"type": "uint256"
			}
		],
		"name": "tokenByIndex",
		"outputs": [
			{
				"internalType": "uint256",
				"name": "",
				"type": "uint256"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "uint256",
				"name": "",
				"type": "uint256"
			}
		],
		"name": "tokennumber",
		"outputs": [
			{
				"internalType": "uint256",
				"name": "",
				"type": "uint256"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "address",
				"name": "owner",
				"type": "address"
			},
			{
				"internalType": "uint256",
				"name": "index",
				"type": "uint256"
			}
		],
		"name": "tokenOfOwnerByIndex",
		"outputs": [
			{
				"internalType": "uint256",
				"name": "",
				"type": "uint256"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [
			{
				"internalType": "uint256",
				"name": "tokenId",
				"type": "uint256"
			}
		],
		"name": "tokenURI",
		"outputs": [
			{
				"internalType": "string",
				"name": "",
				"type": "string"
			}
		],
		"stateMutability": "view",
		"type": "function"
	},
	{
		"inputs": [],
		"name": "totalSupply",
		"outputs": [
			{
				"internalType": "uint256",
				"name": "",
				"type": "uint256"
			}
		],
		"stateMutability": "view",
		"type": "function"
	}
]

//contract instance
contract = new web3.eth.Contract(abi, contractAddress);

// Accounts
var account;

web3.eth.getAccounts(function(err, accounts) {
  if (err != null) {
    alert("Error retrieving accounts.");
    return;
  }
  if (accounts.length == 0) {
    alert("No account found! Make sure the Ethereum client is configured properly.");
    return;
  }
  account = accounts[0];
  console.log('Account: ' + account);
  web3.eth.defaultAccount = account;
});

//Smart contract functions
function mintfunction() {

  contract.methods.balanceOf(account).call().then( function( info ) {
    var tempinfo = info ;
    if(tempinfo == 0) {
      tokenno = $("#tokenno").val();
      contract.methods.mint (tokenno).send( {from: account , value:web3.utils.toWei('0.0001','ether')}).then( function(tx) {
        console.log("Transaction: ", tx);
      });
      $("#tokenno").val('');
    }
    else {
      console.log("You already have an account") ;
    }
  });
}

function balanceofaccount() {
  contract.methods.balanceOf(account).call().then( function( info ) {
    console.log("info: ", info) ;


  var x = document.getElementById("myDIV");
  if (info == 1) {
    x.style.display = "block";
  } else {
    x.style.display = "none";
  }

  });
}