A Guide to Understanding Web3 Ethereum Javascript API Library

Posted By : Bhuvan

Jul 24, 2020

The Web3 .js Ethereum JS Library

Web3.js is a collection and combination of the fullness of Ethereum libraries that enables a developer to interface with a localhost or Ethereum node, using an HTTP connection in your JS file with some given aspects. This web3.js Js library interfaces with the Ethereum blockchain node. Using this library, you can create user accounts and send transactions using from address or to address, better interact with smart contracts, and more.

 

Best BlockChain Library for Front End developer

 

So, we need to do a few steps to get web3 in your javascript. So, we are moving stepwise so have a look around 

 

Installing Web3.JS in Javascript Code

 

 

-Installing Node

 

Install Node js in your system and max version of node 10.16.0

 

 

-Installing Web3.js

Npm install web3    (If you are using any framework like React/Angular/Vue) So you need to installing web3 using this command 

 

 

 

 -For Normal Javascript code, you can use CDN Link 

CDN: https://cdn.jsdelivr.net/gh/ethereum/[email protected]/dist/  (This link provide you a whole library event so you can paste this link into index.html file  

<script src="https://cdn.jsdelivr.net/gh/ethereum/[email protected]/dist/web3.js">

 

Web3  libraries is a repository of modules that contains functionality for the Ethereum node ecosystem. 

-web3.js Object-eth is containing a Ethereum blockchain and smart contracts details.

After Installing web3 into your project, you need to create an instance of Web3. This instance object will help you a lot in the whole project. It provides a collection of modules that contain functionality for the Ethereum Blockchain 

 

For Example : web3.js, Now you can check  that  Web3.givenProvider.

If this object or property  is showing null in console you should connect to a remotely/local node .

const Web3JS = require('web3');

let web3 = new Web3JS(Web3JS.givenProvider || "ws://localhost:8545");
Now you can use Web3 object now they are contain all methods 

 

 

So, now you have finally installed Web3 in your FrontEnd Code. I will now show you some example of how we can use the collections of the module from web3j

(Web3.Js Examples)

 

 

1.Getting Ethereum Node Information 

web3.eth.getNodeInfo(function(error, valueInResult){
      if(error){
         console.log( “error” ,error);
      }
      else{
         console.log( “valueInResult”,valueInResult );  "
      }
 });

 

Also, read | Ethereum Rinkeby Testnet Setup Using Docker Compose

 

2.Getting Balance of your wallet using the address

web3.eth.getBalance : get account’s balance

web3.eth.getAccounts(function(error, accounts) {
  if(error) {
    console.log(error);
  }
  
  web3.eth.getBalance(accounts[0]).then(function(result){
   console.log( "Balance : " ,web3.utils.fromWei(result, 'ether'));
  });
 });
 

 

 

3.Getting Transaction Count Using this Event 

txnCount = web3.eth.getTransactionCount(web3.eth.accounts[0])

 

 

3.How to transfer bitcoins from one address to another address using  

 

Transferring Ether from B to C address

 

txnObject ( transaction object) is first and one argu of web3.eth.sendTransaction and  txnObject is based on JSON Data.  
from: is in string type for adding own address 

to: is in string type for adding sender address 

value: Number|String|BigNumber — (optional) the amount of Ether you wish to send to the from address to address.

gas: Num |String|BigNumber — (optional) the amount of gas is used for transaction and the available amount of gas for the transaction (unused gas is refunded).

gas price: Number|String|BigNumber — (optional)  this is the price of gas for the particular transaction in using web3, default that means is a gas.

 

 

var txnObject = {
        "from":_from,
        "to": _to,
        "value": web3.utils.toWei(_Amount,'ether'),
        ---> this is a option "gas": 23000,      
        ---> this is a option   "gasPrice": 4600000,
        ---> this is a option   "nonce": 11   
     }
   
  web3.eth.sendTransaction(txnObject, function(error, result){
     if(error){
       console.log( "Transaction error" ,error);
     }
     else{
       var txn_hash = result; ---> Get the Transaction hash
     }
  });

 

 

Also, you can Send ICO Token Using this Library 

(Using the same methods )

 

 

My Review about this library 

So, let's talk about my experience with this library. Basically, this library is perfect for using blockchain code in client-side, so this library performs very well but in some cases, they have some disadvantage because they did not allow to own HTTP header in their APIs calls. So, sometimes we are in trouble with that thing, other things are perfect and good. 

 

Also, read | Deploying a Multisignature Wallet Smart Contract on Ethereum

Library Reference Link 

https://web3js.readthedocs.io/en/v1.2.11/index.html

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