bscgo-ethereumweb3web3js
I'm using web3 to get the balance of a single token/contract address within my wallet address.
If I have an array of tokens eg
[
"0x2a9718deff471f3bb91fa0eceab14154f150a385",
"0xad90c05bc51672eedfee36e58b3ff1a78bbc146d",
"0x33a3d962955a3862c8093d1273344719f03ca17c",
"0x85102c0062aa918cb9e26d94a284aafca602df13"
]
Is there a possibility to pass that array into a single call that retrieves the balance for each? Or would we need to iterate through the list one by one?
If you are using web(version 0.19.0: latest stable), you can do
1. Download Web3
bower install web3@0.19.0
2. Algo to load Web3, check the connection and retrieve the accounts
<html>
<body>
<div id="address"></div>
<script src="bower_components/web3/dist/web3.min.js"></script>
<script>
window.addEventListener('load', function() {
// Load WEB3
// Check wether it's already injected by something else (like Metamask or Parity Chrome plugin)
if(typeof web3 !== 'undefined') {
web3 = new Web3(web3.currentProvider);
// Or connect to a node
} else {
web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
}
// Check the connection
if(!web3.isConnected()) {
console.error("Not connected");
}
var account = web3.eth.accounts[0];
var accountInterval = setInterval(function() {
if (web3.eth.accounts[0] !== account) {
account = web3.eth.accounts[0];
document.getElementById("address").innerHTML = account;
}
}, 100);
});
</script>
</body>
</html>
3. Auto-reload after switching account
The solution right now is a basic setInterval function
If you're interested in just a relatively small subset of popular ERC20 tokens, then looping over them might be okay.
But if you want everything, I think your best bet is to process the logs as you go and look for Transfer(address,address,uint256) events. For each event, if the source looks like an ERC20 token (e.g. has name/symbol/decimals), do some accounting in your database where you're keeping track of these things.
Best Answer
You cannot do this through regular JSONRPC calls, but it is possible to limit the number of calls needed by using a smart contract. You can use the library
eth-scanto do this for you. Simply pass in the array of addresses, and it will fetch the balance for each token through theeth-scansmart contract.By default, the library will do a single call for every 1,000 tokens, but this is configurable.
For example:
Disclaimer: I am the author of
eth-scan.