When you build a Ethereum blockchain based JavaScript application you need a way to let your users interact with your application. Metamask is a popular browser extension that enables users to interact with Ethereum blockchain applications. Let us look at some steps to get started with Metamask and a JavaScript applications.
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Install Metamask: The first step is to install the Metamask extension in your browser. You can download it from the official website and follow the instructions to set up your account.
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Connect to a network: Once you have set up your Metamask account, you need to connect it to a network. You can select a network from the dropdown list in the Metamask extension. You can choose from the Ethereum main network, test networks like Ropsten, Rinkeby, or Kovan, or a local network like Ganache.
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Create a new project: Create a new JavaScript project and add the necessary dependencies. You will need to install both the web3 and Metamask provider packages.
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Connect to Metamask: In your JavaScript code, use the web3 library to connect to the Metamask provider. Here's an example code snippet:
This code initializes the web3 library and connects to the Metamask provider. The window.ethereum.enable() method prompts the user to authorize your application to use their Metamask account.
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Interact with the blockchain: Now that you have connected to Metamask, you can interact with the Ethereum blockchain using web3. You can send transactions, read data from the blockchain, and more. Let's look at some code to get the user's account address:
This code uses the web3.eth.getAccounts() method to get the user's account address.
These are the basic steps to get started with Metamask and JavaScript applications. Next, let us look at how we can be sending a transaction using MetaMask and web3.
Let's look at some code!
This code sends a transaction from the user's Metamask account to the specified recipient address with the specified amount. The web3.utils.toWei() method is used to convert the amount from ether to wei, which is the smallest unit of ether.
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The window.ethereum.sendTransaction() method sends the transaction using Metamask. It returns a transaction hash, which can be used to track the status of the transaction. The on('transactionHash') event is triggered when the transaction is broadcasted to the network, and the on('confirmation') event is triggered when the transaction is confirmed by the network. The on('error') event is triggered if there is an error sending the transaction.
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Note that the user must have authorized your application to use their Metamask account before the transaction can be sent. If the user has not authorized your application, you can prompt them to do so using the window.ethereum.enable() method.