Convert `web3` asynchronous calls into Promises.

promisifyWeb3.js

module.exports = {
    promisify: function (web3) {
        // Pipes values from a Web3 callback.
        var callbackToResolve = function (resolve, reject) {
            return function (error, value) {
                    if (error) {
                        reject(error);
                    } else {
                        resolve(value);
                    }
                };
        };

        // List synchronous functions masquerading as values.
        var syncGetters = {
            db: [],
            eth: [ "accounts", "blockNumber", "coinbase", "gasPrice", "hashrate",
                "mining", "protocolVersion", "syncing" ],
            net: [ "listening", "peerCount" ],
            personal: [ "listAccounts" ],
            shh: [],
            version: [ "ethereum", "network", "node", "whisper" ]
        };

        Object.keys(syncGetters).forEach(function(group) {
            Object.keys(web3[group]).forEach(function (method) {
                if (syncGetters[group].indexOf(method) > -1) {
                    // Skip
                } else if (typeof web3[group][method] === "function") {
                    web3[group][method + "Promise"] = function () {
                        var args = arguments;
                        return new Promise(function (resolve, reject) {
                            args[args.length] = callbackToResolve(resolve, reject);
                            args.length++;
                            web3[group][method].apply(web3[group], args);
                        });
                    };
                }
            });
        });
    },
};

You can use it like so:

web3.eth.getTransactionPromise(txHash)
    .then(function(tx) {
        console.log(tx);
    });

You prepare it like so:

const PromisifyWeb3 = require("./promisifyWeb3.js");
PromisifyWeb3.promisify(web3);

Hi @xavierlepretre, thanks for sharing your contributions... I'm quite newbie with js dev, and now dealing and learning all about this upgraded version of Web3 with promises and calls... I'm trying to test your gists, seem to be very useful to deal with all these new web3 features. I'm developing adding the sources to my HTML and developing code in a separate myscript.js.
I started with the following code (I have a private network running with some basic contracts)

     var web3 = new Web3(new Web3.providers.HttpProvider("http://myLocalHostIP:myRpcPort"));
     PromisifyWeb3.promisify(web3);

I get: ReferenceError: PromisifyWeb3 is not defined[Learn More]
How should I call properly your functions?
I would also like to understand what to replace with in txHash? in the implementation web3.eth.getTransactionPromise(txHash).. may be any eth command like eth.sendTransaction({from: eth.accounts[0], to: eth.accounts[1], value: web3.toWei(3,"ether")})..
Thanks for your guidance...

@renexdev You have to import PromisifyWeb3 like @xavierlepretre mentioned in the post above yours:

const PromisifyWeb3 = require("./promisifyWeb3.js");
PromisifyWeb3.promisify(web3);