Simple Tutorial using INFURA and the JavaScript Web3 APIHappy Labor Day to our U.S.In that spirit, why not let INFURA take the work load off of your shoulders when it comes to your Ethereum Dapp development?Let’s take a quick look at how to get started today.Step One: RegisterINFURA is free to use, but you do need to identify your requests sent to our RPC provider endpoints.For that, you need an Access Token.Getting an Access Token is quick and easy.Just visit the INFURA Registration page to quickly register to use our service.INFURA Registration FormYou will notice that the only required field for you to provide is an email address.We will use your email only to provide critical communication regarding service changes in the future that may impact your usage of the service.You can also opt to join our mailing list for ongoing communications and updates of a less critical nature.The rest of the form is optional, however we would really like to hear about how you plan to use our service so we can tailor it to meet your needs as we map out the roadmap.

I encourage you to share as much information about your project as you are comfortable with.After submitting your registration, you will be given information on how to access INFURA.ethereum tutorial youtubeIt will look something like this:INFURA Welcome NoteThe blurred out part will be your unique Access Token.bitcoin fork dayYou’ll also notice that for now, IPFS has no identification mechanism on the URL.Notice that our INFURA provider URLs are all over SSL.ethereum armMake sure you use https:// when you send requests to INFURA rather than http:// requests.paras bitcoin lompakkoAlso note, there is no port on the URL.bitcoin hmrc

Our listener is on the standard HTTPS port 443.If for any compatibility reason you need to send requests to INFURA on the standard JSON-RPC port 8545, we support that too, just make sure the HTTP protocol you are using is HTTPS.To our curious user, you might quickly recognize that INFURA works just fine without adding the Access Token to the URL.5 gh/s bitcoin miner bitcoinThat is only partially true.bitcoin slaveWhile INFURA will work without identifying your requests, these requests will be subjected to more restrictive throttling and filtering of available JSON-RPC methods.Now that you have your provider URLs, let’s get started making a few requests.INFURA behaves just like a local install of Ethereum running RPC.ethereum wallet androidFor a complete set of documentation on the JSON-RPC methods available, you can read the official documentation here.Let’s see how to send a few requests via HTTPS POST using curl.is bitcoin mining bad for your gpu

If you are using Linux or Mac OS X, open a Terminal.Windows users will need to download and install curl.What client and version is INFURA running?From the Terminal, enter this command.Remember to replace ‘MEDIUMTUTORIAL’ with your own unique Access Token from Step One.JSON-RPC Example using curl to query INFURA Ethereum client and versionThis is identical to the official documentation for the web3_clientVersion method, just using your unique INFURA provider URL.You’ll notice the data returned tells you that INFURA is running Geth/v1.4.11-stable/linux/go1.6.2.It is on our roadmap to support many more clients in the future.Easy right?Let’s try one more.What is the latest Ethereum Block that INFURA has seen?For this, we can call the eth_blockNumber method.From the Terminal, enter this command.Again, replace ‘MEDIUMTUTORIAL’ with your own unique Access Token.JSON-RPC Example using curl to query INFURA Ethereum latest block numberThe result from eth_blockNumber is “0x21a134”.

Recall that data passed to and from the HTTP JSON-RPC provider is hexadecimal encoded.Use a converter to convert that to decimal and we see that 0x21a134 in decimal is 2,203,956.That looks more like a block number we would expect!Using curl, we can easily query and post data to the Ethereum blockchain using interactive commands.What if we want to integrate this into a web application?UPDATE: since the publication of this article, the backend has gotten a little more strict in the valid requests it will accept.Therefore, you will need to supply the Content-Type for the POST request as application/json.See below for an up-to-date working example:curl -X POST --data '{"jsonrpc":"2.0","method":"web3_clientVersion","params":[],"id":67}' -H "Content-Type: application/json" https://mainnet.infura.ioThe Web3 Javascript API is a very useful library that gives you an API to the Ethereum blockchain from within Javascript allowing you to build feature-rich web applications that are able to interact with Ethereum.To demonstrate how quickly you can build a web application, let’s build an Ethereum Account Explorer.

Our explorer will do two things, it will print out the block number of the latest block and it will show the balance in Ether for a supplied Ethereum account.Let’s start with a simple HTML for our explorer.HTML Template for Ethereum Account Explorer built on INFURAThe HTML is quite simple.An input field to submit an account that we want to check the balance on, and a few placeholders for where we will print the latest block and the balance of the submitted account.The corresponding HTML follows.Now let’s start adding in the Javascript.First, we need to include the Web3 javascript library.This gives us access to the Web3 API as documented here.Next, we will create a new object called web3 that is an instantiation of Web3.As we do this, we establish our HTTP Web3 provider, that acts as the backend for all of our method calls against that object.This is where INFURA comes in!For the purposes of this tutorial, I am leaving out important error handling logic.For your application, I strongly recommend you review the code shown in the documentation for adding a web3 provider.So far, nothing visible on our page has changed.

Now that we have included the Web3 API and instantiated a web3 object.We can begin to interact with the Ethereum blockchain.First, let’s add the latest block number to our page using web3.eth.blockNumber.Let’s take a look at what a visitor to our page sees now.OK, that was pretty easy, right?Now for the last piece, let’s allow the customer to enter an account in the form.To do this, we will create a function called printAccountBalance().There is a lot going on there, so let’s walk through it.The first 10 lines of the function are there so that we can get the value submitted in the form in the account Javascript variable.You don’t need to worry too much about that if you are unfamiliar with Javascript.From there, now that we have the submitted account available in our function, we can use a few web3 methods.First, we call web3.eth.getBalance(account).toNumber().Per the documentation, we pass an Ethereum Address (account) and it returns a string representing the value in wei, which is the smallest denomination of Ether.

We have that value stored in the variable balanceWei, however it is a string.We need to convert that to Ether so will need that value as a number…so we use the method .toNumber() to make that conversion.The web3.fromWei(number, unit) method is a quick and useful way to convert a value in Wei to any other denomination of Ether.We want to know what the value is of balanceWei in Ether, so we use: web3.fromWei(balanceWei, ‘ether’).We now have a variable called balance that has the account balance in Ether of the provided account.The last two lines of the function print those values out to the web page.The last step is to add the code to call our newly created printAccountBalance() function.With that, let’s take a look at the entire block of code we have put together thus far.Now that all of our code is in place, let’s give it a try.Let’s use our newly built Account Explorer to check the balance of the Ethereum Account that belongs to EthDev: 0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe.Wow!