web3-service-loader.js

/**
 * To anyone using this class.
 * Web3ServiceLoader is a singleton factory 
 * web3js wants to live in the global space and the exports for it tend to come and go.
 * We ignore the global web3 because it could be put there by anything including MetaMask which frequently uses a very outdated version of web3
 * Most users of this service are building wallets and tools to interact with their own dapps and it is important the latest stable features are made available to them
 * 
 * What we have here is...
 * Web3ServiceLoader which is a static class with a single static method
 * The single static method is getInstance and it accepts a provider as an argument.
 * We highly recommend infura.io for this
 * 
 * When you call Web3ServiceLoader.getInstance(provider) for the very first time, it will load web3.min.js
 * It will then instantiate a new Web3 instance with the provider you pass in and return the new instance.
 * 
 * From there, any subsequent calls to getInstance() will return the same web3js instance
 * 
 * In order to prevent chaos, you should only use the service loader in a single place in your app
 * 
 * For telepathy this should be in your app root and should be called only once by the onReady method.
 * If you import this in multiple places you could get unpredictable behavior, however we try to guard against it by attaching ourselves to window
 * Nevertheless, telepathy is blindingly fast and multi-threaded, 
 * therefore it's possible to get multiple web3 instances all going at once if you are importing this script all over the place
 */

export class Web3ServiceLoader {
    static async getInstance(provider){
        console.log("Web3Service entering getInstance with ",provider);
        if(!window.Web3Service){
            window.Web3Service = Web3ServiceLoader;
        }
        if(!window.Web3Service.loading){
            window.Web3Service.loading = true;
            if(!Web3ServiceLoader.instance){
                let data = await (await fetch("https://telepathic-elements.github.io/web3-service-loader/web3.min.js")).text();
                await eval(data);
                Web3ServiceLoader.instance = await new Web3(provider);
            }
            window.Web3Service.loading = false;
        }
        console.log("Web3Service leaving getInstance");
        return Web3ServiceLoader.instance;
    }
};