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Moved web3 tutorial into main, for merge as appendix
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@aantonop
aantonop committed May 14, 2018
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163 changes: 163 additions & 0 deletions web3-contract-basic-interaction-async-await.asciidoc
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== web3.js contract basic interaction (async/await) as if they were synchronous functions

=== Description
This script is for educational use and is based on web3@1.0.0-beta.29 web3.js version.

It should be see as an introduction to web3.js.

The web3.js library is a collection of modules which contain specific functionality for the Ethereum ecosystem.

The web3.js object is an umbrella package to house all Ethereum related modules.

This is the Ethereum compatible JavaScript API which implements the Generic JSON RPC spec.

It run in a blocked (async/await) mode to move the reader away from the hell of the Promises as long as their version of nodejs or javascript allows it.

The most remarkable thing about this script is that you don’t need to run your own local node to use it, because it use the https://infura.io[Infura services].

=== Prepare the environment
To see this script in action you should follow this simple steps.

==== Check you have a valid npm version
----
$ npm -v
5.6.0
----

==== If you don't have already done, initialize your package
----
$ npm init
----

==== Install basic dependences
----
npm i web3
npm i node-rest-client-promise
----

This will update your package.json cofiguracion file with your new dependences.

==== Node.js script execution

Execution example;
----
code/web3js/./web3-contract-basic-interaction-async-await.js
----

== What the hell this script do?
This script try to introduce to the basic use of web3.js using async/await (less Code), as if they were synchronous functions that return values ​​directly instead of promises.

=== web3 provider
We use web3.js Web3 object to obtain a basic web3 provider.

----
var web3 = new Web3(infura_host);
----

=== Let's do some basic interactions at web3 level
Let's get the Protocol Version.

----
var protocolVersion = await web3.eth.getProtocolVersion();
----

Now I'm curious about the current gas price.

----
var gasPrice = await web3.eth.getGasPrice();
----

And, Whats the last mined block in my chain?

----
var blockNumber = await web3.eth.getBlockNumber();
----

=== Now let's dive into some basics actions with a contract
We will use the contract at;
https://kovan.etherscan.io/address/0xd0a1e359811322d97991e03f863a0c30c2cf029c#code

First things first, let's initialize our contract address.

----
var our_contract_address = "0xd0A1E359811322d97991E03f863a0C30C2cF029C";
----

Let's get its balance.

----
var balance = await web3.eth.getBalance(our_contract_address);
----

Now let's get its byte code.

----
var code = await web3.eth.getCode(our_contract_address);
----

=== Now we are going to deal with the contract
We prepare our environment to interact with the Etherescan explorer API.

Let's initialize our contract url in the Etherescan explorer API for the Kovan chain.

----
var etherescan_url = `http://kovan.etherscan.io/api?module=contract&action=getabi&address=${our_contract_address}`
----

And now get a rest client to operate with.

----
var client = require('node-rest-client-promise').Client();
----

Let's get the client response.

----
var etherescan_response = await client.getPromise(etherescan_url)
----

Now we get here our contract ABI from the client response (from the Etherescan explorer).

----
our_contract_abi = JSON.parse(etherescan_response.data.result);
----

Let's instantiate our contract object

----
var our_contract = await new web3.eth.Contract(our_contract_abi, our_contract_address);
----

Let's see our contract address.
----
console.log(`Our Contract address: ${our_contract._address}`);
----

or in this other way.
----
console.log(`Our Contract address in other way: ${our_contract.options.address}`);
----

Now our contract abi.
----
console.log("Our contract abi: " + JSON.stringify(our_contract.options.jsonInterface));
----

=== This is turning more interesting, let's see what's going on with our contract
Now let's get our contract total supply.

----
var totalSupply = await our_contract.methods.totalSupply().call();
----

Now let's get our contract public variable name.

----
var name = await our_contract.methods.name().call();
----

Now let's get our contract public variable symbol.

----
var symbol = await our_contract.methods.symbol().call();
----
206 changes: 206 additions & 0 deletions web3-contract-basic-interaction.asciidoc
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== web3.js Contract basic interaction in a non-blocked (async) fashion

=== Description
This script is for educational use and is based on web3@1.0.0-beta.29 web3.js version.

It should be see as an introduction to web3.js.

The web3.js library is a collection of modules which contain specific functionality for the Ethereum ecosystem.

The web3.js object is an umbrella package to house all Ethereum related modules.

This is the Ethereum compatible JavaScript API which implements the Generic JSON RPC spec.

It run in a non-blocked (async) mode to accommodate in many of the methods provided by web3.js

The most remarkable thing about this script is that you don’t need to run your own local node to use it, because it use the https://infura.io[Infura services].

Anyway, I could adapt this script to be used with a local running node if it seems interesting.

=== Prepare the environment
To see this script in action you should follow this simple steps.

==== Check you have a valid npm version
----
$ npm -v
5.6.0
----

==== If you don't have already done, initialize your package
----
$ npm init
----

==== Install basic dependences
----
npm i command-line-args
npm i web3
npm i node-rest-client-promise
----

This will update your package.json cofiguracion file with your new dependences.

==== Node.js script execution

Basic execution
----
code/web3js/web3-contract-basic-interaction.js
----

Use your own Infura Token
----
code/web3js/web3-contract-basic-interaction.js --infuraFileToken /path/to/file/with/infura_token
or
code/web3js/web3-contract-basic-interaction.js /path/to/file/with/infura_token
----

== What the hell this script do?
This script try to introduce to the basic use of web3.js

Despite some utilities provided by the script what it really do is ...

=== web3 provider
We use web3.js Web3 object to obtain a basic web3 provider.

----
var web3 = new Web3(infura_host);
----

=== Let's do some basic interactions at web3 level
Let's see the Protocol Version.

----
web3.eth.getProtocolVersion().then(function(protocolVersion) {
console.log(`Protocol Version: ${protocolVersion}`);
})
----

Now I'm curious about the current gas price.

----
web3.eth.getGasPrice().then(function(gasPrice) {
console.log(`Gas Price: ${gasPrice}`);
})
----

And, Whats the last mined block in my chain?

----
web3.eth.getBlockNumber().then(function(blockNumber) {
console.log(`Block Number: ${blockNumber}`);
})
----

=== Now let's dive into some basics actions with a contract
We will use the contract at;
https://kovan.etherscan.io/address/0xd0a1e359811322d97991e03f863a0c30c2cf029c#code

First things first, let's initialize our contract address.

----
var our_contract_address = "0xd0A1E359811322d97991E03f863a0C30C2cF029C";
----

Let's see its balance.

----
web3.eth.getBalance(our_contract_address).then(function(balance) {
console.log(`Balance of ${our_contract_address}: ${balance}`);
})
----

Now let's see its byte code.

----
web3.eth.getCode(our_contract_address).then(function(code) {
console.log(code);
})
----

=== Now we are going to deal with the contract
We prepare our environment to interact with the Etherescan explorer API.

Let's initialize our contract url in the Etherescan explorer API for the Kovan chain.

----
var etherescan_url = `http://kovan.etherscan.io/api?module=contract&action=getabi&address=${our_contract_address}`
----

And now get a rest client to operate with.

----
var client = require('node-rest-client-promise').Client();
----

Let's get a client promise.

----
client.getPromise(etherescan_url)
----

And once we got a valid client promise, then we can use it.

Now we get here our contract ABI from the client promise (from the Etherescan explorer).
----
.then((client_promise) => {
our_contract_abi = JSON.parse(client_promise.data.result);
----

And now we create our contract object as a promise to consume later.
----
return new Promise((resolve, reject) => {
var our_contract = new web3.eth.Contract(our_contract_abi, our_contract_address);
try {
// If all goes well
resolve(our_contract);
} catch (ex) {
// If something goes wrong
reject(ex);
}
});
})
----

If our contract promise return well let's consume it.
----
.then((our_contract) => {
----

Let's see our contract address.
----
console.log(`Our Contract address: ${our_contract._address}`);
----

or in this other way.
----
console.log(`Our Contract address in other way: ${our_contract.options.address}`);
----

Now our contract abi.
----
console.log("Our contract abi: " + JSON.stringify(our_contract.options.jsonInterface));
----

=== This is turning more interesting, let's see what's going on with our contract
Now let's see our contract total supply in a callback fashion;

----
our_contract.methods.totalSupply().call(function(err, totalSupply) {
if (!err) {
console.log(`Total Supply with a callback: ${totalSupply}`);
} else {
console.log(err);
}
});
----

Or you can use the returned Promise instead of passing in the callback;
----
our_contract.methods.totalSupply().call().then(function(totalSupply){
console.log(`Total Supply with a promise: ${totalSupply}`);
}).catch(function(err) {
console.log(err);
});
----

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