How to call Web3js function from Nodejs file - node.js

Question

I have the following working web3js code, Calling App.createContract() on button click works well on a webpage, however I want to call App.createContract() or similar from another Nodejs controller. Infact what I am thinking of is making an API in Node which could call the web3js function and returns a JSON result back to the caller. Can you please help me how to import my web3js file and call the function from Node Controller? Thanks
import "../stylesheets/app.css";
import { default as Web3} from 'web3';
import { default as contract } from 'truffle-contract';
import { default as CryptoJS} from 'crypto-js';
var accounts;
var account;
var shLogABI;
var shLogContract;
var shLogCode;
var shLogSource;
window.App = {
start: function() {
var self = this;
web3.eth.getAccounts(function(err, accs) {
if (err != null) {
alert("There was an error fetching your accounts.");
return;
}
if (accs.length == 0) {
alert("Couldn't get any accounts! Make sure your Ethereum client is configured correctly.");
return;
}
accounts = accs;
console.log(accounts);
account = accounts[0];
web3.eth.defaultAccount= account;
shLogSource= "pragma solidity ^0.4.6; contract SHLog { struct LogData{ string FileName; uint UploadTimeStamp; string AttestationDate; } mapping(uint => LogData) Trail; uint8 TrailCount=0; function AddNewLog(string FileName, uint UploadTimeStamp, string AttestationDate) { LogData memory newLog; newLog.FileName = FileName; newLog.UploadTimeStamp= UploadTimeStamp; newLog.AttestationDate= AttestationDate; Trail[TrailCount] = newLog; TrailCount++; } function GetTrailCount() returns(uint8){ return TrailCount; } function GetLog(uint8 TrailNo) returns (string,uint,string) { return (Trail[TrailNo].FileName, Trail[TrailNo].UploadTimeStamp, Trail[TrailNo].AttestationDate); } }";
web3.eth.compile.solidity(shLogSource, function(error, shLogCompiled){
shLogABI = JSON.parse(' [ { "constant": false, "inputs": [ { "name": "TrailNo", "type": "uint8" } ], "name": "GetLog", "outputs": [ { "name": "", "type": "string" }, { "name": "", "type": "uint256" }, { "name": "", "type": "string" } ], "payable": false, "type": "function" }, { "constant": false, "inputs": [ { "name": "FileName", "type": "string" }, { "name": "UploadTimeStamp", "type": "uint256" }, { "name": "AttestationDate", "type": "string" } ], "name": "AddNewLog", "outputs": [], "payable": false, "type": "function" }, { "constant": false, "inputs": [], "name": "GetTrailCount", "outputs": [ { "name": "", "type": "uint8" } ], "payable": false, "type": "function" } ]');
shLogContract = web3.eth.contract(shLogABI);
});
});
},
createContract: function()
{
shLogContract.new("", {from:account, gas: 3000000}, function (error, deployedContract){
if(deployedContract.address)
{
document.getElementById("contractAddress").value=deployedContract.address;
document.getElementById("fileName").value = '';
document.getElementById("uploadTimeStamp").value = '';
document.getElementById("attestationDate").value = '';
}
})
},
addNewLog: function()
{
var contractAddress = document.getElementById("contractAddress").value;
var deployedshLog = shLogContract.at(contractAddress);
var fileName = document.getElementById("fileName").value;
var uploadTimeStamp = document.getElementById("uploadTimeStamp").value;
var attestationDate = document.getElementById("attestationDate").value;
deployedshLog.AddNewLog(fileName, uploadTimeStamp, attestationDate, function(error){
console.log(error);
})
},
getLog: function()
{
try{
var contractAddress = document.getElementById("contractAddress").value;
var deployedshLog = shLogContract.at(contractAddress);
deployedshLog.GetTrailCount.call(function (error, trailCount){
deployedshLog.GetLog.call(trailCount-1, function(error, returnValues){
document.getElementById("fileName").value= returnValues[0];
document.getElementById("uploadTimeStamp").value = returnValues[1];
document.getElementById("attestationDate").value=returnValues[2];
})
})
}
catch (error) {
document.getElementById("fileName").value= error.message;
document.getElementById("uploadTimeStamp").value = error.message;
document.getElementById("attestationDate").value= error.message;
}
}
};
window.addEventListener('load', function() {
if (typeof web3 !== 'undefined') {
console.warn("Using web3 detected from external source. If using MetaMask, see the following link. Feel free to delete this warning. :) http://truffleframework.com/tutorials/truffle-and-metamask")
window.web3 = new Web3(web3.currentProvider);
} else {
console.warn("No web3 detected. Falling back to http://localhost:8545. You should remove this fallback when you deploy live, as it's inherently insecure. Consider switching to Metamask for development. More info here: http://truffleframework.com/tutorials/truffle-and-metamask");
// fallback - use your fallback strategy (local node / hosted node + in-dapp id mgmt / fail)
window.web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
}
App.start();
});

Answer 1

Simple example for web3js 1.0.0.beta*
1) Add web3js to your package.json on a server side:
"web3": "^1.0.0-beta.27"
2) Require and init web3 with some provider:
const Web3 = require('web3');
const web3SocketProvider = new Web3.providers.WebsocketProvider('ws://0.0.0.0:8546');
const web3Obj = new Web3(web3Provider);
Now you can use your web3 object as usual:
async function getAccounts() {
let accounts = await web3Obj.eth.getAccounts();
}