Lesson 7 - Javascript Syntax Question

[alkali333]

Hi there,

Can somebody please give me a plain English explanation of the following code in 001-deploy-fund-me.js

module.exports = async ({ getNamedAccounts, deployments }) => {
    const { deploy, log } = deployments
    const { deployer } = await getNamedAccounts()
    const chainId = network.config.chainId
}

I'm confused by the syntax and also it seems there is a lot going on behind the scenes with hardhat and the deploy plugin.

[krakxn]

{ getNamedAccounts, deployments } is just a shorthand for const { getNamedAccounts, deployments } = hre

The above essentially "extracts" getNamedAccounts and deployments from Hardhat

async declares the function as an asynchronous one, which lets us use await

Further, for it to be used in other scripts, we have to declare it as a "module", i.e. module.exports (this is a Node.js thing, you will comprehend when you go through a Node.js course, but for now just know that it is a module primarily used for exporting, which can then be used in other scripts)

const { deploy, log } = deployments

Similarly, the above "extracts" deploy and log from deployments

const { deployer } = await getNamedAccounts()

In hardhat.config:

namedAccounts: {
        deployer: {
            default: 0,
        },

so, getNamedAccounts is just a getter provided to us. Out of which, we "extract" deployer

const chainId = network.config.chainId

This is equivalent to, network->config->chainId for accessing the chainId.

Refer https://hardhat.org/hardhat-network/docs/reference#config

[alkali333]

Thanks for the in-depth explanation, it has helped a lot. The hre was the main thing that I was missing, Since I'm not familiar with node.js it sometimes is hard for me to figure out where various functions are coming from - I'll definitely do a node.js course after this. The module exports thing seems pretty central to all of this, and I'm starting to get it!

[krakxn]

There is not much to it, just the specification for exporting is different relative to vanilla JS. Besides that there is no difference, and even if you do a Node.js course, it will be more for networking back-end.

[othaime-en]

Okay. In the first line we are creating an asyncronous function, and exporting it. This is the same as creating a function and exporting it

async function main() {}
module.exports = main

However, how hardhat-deploy works is that, we pass in an instance of the hardhat-runtime-environment/hre ( same as doing require("hardhat") ) when creating this function. which will be like

async function main(hre) {}
module.exports = main

But then instead of passing the entire hre, we only want two objects from hre that is getNamedAccounts and deployments, so we extract them using the {getNamedAccounts, deployments} notation which is basically the same as doing hre.deployments or hre.getNamedAccounts
Afterwards, since these two objects also have several attributes/functionalities inside them, we also want specific functions out of them. So we use the same notation as we did above, and extract deploy and log out of the deployments object. Again, this is the same as doing

const deploy = deployments.deploy  // which is also the same as hre.deployments.deploy
const log = deployments.log  // also the same as hre.deployements.log

[alkali333]

Thanks for breaking it down like that. So the first line is like a shorthand way of creating and exporting the function that has been passed the bits of the hre that it needs. It seems I have jumped in the deep end a bit with node.js, but you've made it clear by showing the longhand ways of doing stuff. I'll try and pick up the syntax the best I can for now then do a node.js course to bring me up to speed.

[othaime-en]

Atleast now you have a basic idea of what is happening. Doing a nodejs course wont be that challenging since mostly javascript along with some of the things we are doing in this course. Wishing you good luck.