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Metamask: Web3 JS (MetaMask Ext and Metamask Mobile)

Published by Terlumun Aondover on February 13th, 2025.

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Metamask: Web3.js – Extender and Mobile App

As a React developer building decentralized applications (dApps) on the Ethereum blockchain, you’re likely familiar with the importance of secure communication between your front-end and back-end. One crucial aspect is ensuring that your contract functions are called successfully from within your application.

In this article, we’ll delve into how to use Metamask, a popular Web3.js extender for React applications, to call contract functions on your local Ethereum testnet or mainnet.

What is Metamask?

Metamask is an open-source browser extension that allows users to interact with the Ethereum blockchain directly in their web browsers. It provides an easy-to-use interface for sending and receiving Ether (ETH), as well as interacting with various contract functions.

Why Call Contract Functions Using Metamask?

Calling contract functions on your local testnet or mainnet can be useful for testing, development, or even production deployment. However, it’s essential to note that calling contract functions directly from a browser extension might not work due to security and compatibility issues.

Here are some scenarios where you might want to call contract functions using Metamask:

Testing decentralized applications: If you’re building a dApp on the Ethereum blockchain, Metamask can help you test your application’s functionality without having to set up an external network.

Development environment: You can use Metamask to interact with local tests or development networks to test contract functions before deploying them to a live chain.

Production deployment: If you’re planning to deploy your dApp on the mainnet, it’s essential to ensure that your contract functions are called successfully. Metamask can help you achieve this by providing a secure interface for interacting with your contract.

Metamask Extender and Metamask Mobile App

The Metamask extender is a lightweight browser extension that allows you to access the Ethereum blockchain in your web browser. It’s available for Chrome, Firefox, Safari, and Microsoft Edge. Once installed, you can use the Metamask extender to interact with your contract functions.

How to Call Contract Functions Using Metamask

Metamask: Web3 JS (MetaMask Ext and Metamask Mobile)

To call contract functions using Metamask, follow these steps:

Install the Metamask extender: Download and install the Metamask extender from the official website.

Open the extender settings: Click on the three dots (⋯) next to your browser icon in the address bar, then select “Settings.”

Select the testnet or mainnet: Choose the Ethereum network you want to use (e.g., Ropsten Testnet or Rinkeby Mainnet).

Create a new wallet: Create a new Wallet or use an existing one.

Install the MetaMask Web SDK: The MetaMask extender provides a Web SDK for interacting with your contract functions. You’ll need to install this JavaScript library in your React application.

Here’s an example of how you can call a contract function using Metamask in your React component:

“`jsx

import React, { useState } from ‘react’;

import metamaskWebSdk from ‘@metamask/web-sdk’;

const Web3 = metamaskWebSdk;

function MyComponent() {

const [contractAddress, setContractAddress] = useState(‘0x…’);

const callFunction = async () => {

try {

// Call contract function using Metamask

const web3 = new Web3(metamaskWebSdk);

const account = await metamaskWebSdk.getAccounts().find((account) => account.address === contractAddress);