Example Code

Example Code to link Blockchain network to your Web

For Solidity Code,

See attached folder, annotation is written for every function.

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Users make their own cryptocurrency wallets on the Web, put coins in their wallets in any way, and donate them.

As a simple example, you can see by using "metamask", which creates a "seed" of 12 random words for each user before making a user's wallet. "Seed" becomes the user's unique code and identifies the user.

So, how do we make seeds and wallets in our project? How do we make them available in blockchain networks?

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We use the "Web3", Ethereum JavaScript API, which connects our Web to the blockchain network, and the LightWallet library for wallet generation.

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In the code below,

generate_seed() : Generate the user's seed.

generate_addresses(seed) : To the user of the seed, make a wallet that can be used in the blockchain and return the address of the wallet.

send_ether() : When a user enters the recipient's wallet address, his or her wallet address, and the coin to be donated from the web, the transaction is made and the transaction address is returned.

function generate_seed()
{
   var new_seed = lightwallet.keystore.generateRandomSeed();

   document.getElementById("seed").value = new_seed;

   generate_addresses(new_seed);
}

var totalAddresses = 1;

function generate_addresses(seed)
{
   if(seed == undefined)
   {
      seed = document.getElementById("seed").value;
   }

   if(!lightwallet.keystore.isSeedValid(seed))
   {
      document.getElementById("info").innerHTML = "Please enter a valid seed";
      return;
   }

   

   if(!Number.isInteger(parseInt(totalAddresses)))
   {
      document.getElementById("info").innerHTML = "Please enter valid number of addresses";
      return;
   }

   var password = Math.random().toString();

   lightwallet.keystore.createVault({
      password: password,
        seedPhrase: seed
   }, function (err, ks) {
        ks.keyFromPassword(password, function (err, pwDerivedKey) {
          if(err)
          {
             document.getElementById("info").innerHTML = err;
          }
          else
          {
             ks.generateNewAddress(pwDerivedKey, totalAddresses);
             var addresses = ks.getAddresses();   
             
             var web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));

             var html = "";

             for(var count = 0; count < addresses.length; count++)
             {
               var address = addresses[count];
               var private_key = ks.exportPrivateKey(address, pwDerivedKey);
               var balance = web3.eth.getBalance("0x" + address);

               html = html + "<li>";
               html = html + "<p><b>Address: </b>0x" + address + "</p>";
               html = html + "<p><b>Private Key: </b>0x" + private_key + "</p>";
               html = html + "<p><b>Balance: </b>" + web3.fromWei(balance, "ether") + " ether</p>";
                html = html + "</li>"; 
             }

             document.getElementById("list").innerHTML = html;
          }
        
      });
   });
}

function send_ether()
{
   var   seed = document.getElementById("seed").value;

   if(!lightwallet.keystore.isSeedValid(seed))
   {
      document.getElementById("info").innerHTML = "Please enter a valid seed";
      return;
   }

   var password = Math.random().toString();

   lightwallet.keystore.createVault({
      password: password,
        seedPhrase: seed
   }, function (err, ks) {
        ks.keyFromPassword(password, function (err, pwDerivedKey) {
          if(err)
          {
             document.getElementById("txnhash").innerHTML = err;
          }
          else
          {
             ks.generateNewAddress(pwDerivedKey, totalAddresses);

             ks.passwordProvider = function (callback) {
                  callback(null, password);
             };

             var provider = new HookedWeb3Provider({
                 host: "http://localhost:8545",
                 transaction_signer: ks
            });

             var web3 = new Web3(provider);

             var from = document.getElementById("address1").value;
            var to = document.getElementById("address2").value;
             var value = web3.toWei(document.getElementById("ether").value, "ether");

             web3.eth.sendTransaction({
                from: from,
                to: to,
                value: value,
                gas: 21000
             }, function(error, result){
                if(error)
                {   
                   document.getElementById("txnhash").innerHTML = error;
                }
                else
                {
                   document.getElementById("txnhash").innerHTML = "Txn hash: " + result;
                }
             })
          }
        });
   });
}