What is the logic behind the variables put in {}/extrapolated variables?

[cipher222]

As I get further into the tutorial, I keep getting confused about the "extrapolation" of different variables. I understand what it does but am wondering what the logical reasoning behind this syntactical sugar is. Also, what is this method of extrapolation called?

Here is some of the confusing code:

module.exports = async ({ getNamedAccounts, deployments }),
const { networkConfig } = require("../helper-hardhat-config"),
const { network } = require("hardhat"),
const { deployer } = await getNamedAccounts.

basically, everything that uses {} when declaring a variable/parameter.

Thanks!!

[PatrickAlphaC]

This is actually called Object Destructuring in javascript(sorry, I think I called it extrapolation).

Example 1

On this line:

module.exports = async ({ getNamedAccounts, deployments }),

When we call yarn hardhat deploy, we actually pass an hre or "hardhat runtime environment" variable to the async function described here. So you could think of it as doing:

module.exports = async (hre) {

Now, the hre object has 2 objects we care about, namely getNamedAccounts and deployments. Since we know we only want those, we can just pull them out of hre, or "destructure" them like so:

module.exports = async (hre) {
  { getNamedAccounts, deployments } = hre

Javascript actually just allows us to do it right in the parameters though, like so:

module.exports = async ({ getNamedAccounts, deployments }){

Example 2

For

const { networkConfig } = require("../helper-hardhat-config")

We have a variable named networkConfig in our helper-hardhat-config file. We only want that variable and don't care about the rest of the file. If we wanted, we could just import the whole file, and then just grab the networkConfig variable/object like so:

const helperHardhatConfig = require("../helper-hardhat-config")
const networkConfig = helperHardhatConfig.networkConfig

or

const helperHardhatConfig = require("../helper-hardhat-config")
const {networkConfig} = helperHardhatConfig

or

const {networkConfig} = require("../helper-hardhat-config")

And then it's the same idea for the other examples.

[PatrickAlphaC]

Let me know if this makes sense.

[cipher222]

Yes, this makes sense. Also, Thank you so much for putting all of this together and being so interactive with your community. You are really inspiring to a young developer like me.

[mattjaf]

Thank you for this!! very well written

is it possible to glob it with a * ? like in python, j/w