How can I store the value of a promise and use it once resolved? - node.js

Question

I am currently developing an app which interacts with uniswap, and I have developed a Wrapper class to contain the info and variables I'll need about some pair (e.g DAI/WETH).
As some of this values are asynchronous, I have coded a build() async function to get those before calling the constructor, so I can store them. I want to store the result of this build function, which is an instance of the class I have defined, inside a variable to use it later, but I need to know whether the Promise that that build function returns is resolved before using it, so how can I make it?
Here is the code of the class:
'use strict'
const { ChainId, Fetcher, WETH, Route, Trade, TokenAmoun, TradeType, TokenAmount } = require('#uniswap/sdk')
const { toChecksumAddress } = require('ethereum-checksum-address')
const Web3 = require('web3')
const web3 = new Web3()
const chainId = ChainId.MAINNET;
let tok1;
let tok2;
let pair;
let route;
let trade;
class UniswapTokenPriceFetcher
{
constructor(async_params)
{
async_params.forEach((element) => {
if (element === 'undefined')
{
throw new Error('All parameters must be defined')
}
});
this.trade = async_params[0];
this.route = async_params[1];
this.pair = async_params[2];
this.tok1 = async_params[3];
this.tok2 = async_params[4];
}
static async build(token1, token2)
{
var tok1 = await Fetcher.fetchTokenData(chainId, toChecksumAddress(token1))
var tok2 = await Fetcher.fetchTokenData(chainId, toChecksumAddress(token2))
var pair = await Fetcher.fetchPairData(tok1, tok2)
var route = new Route([pair], tok2)
var trade = new Trade(route, new TokenAmount(tok2, web3.utils.toWei('1', 'Ether')), TradeType.EXACT_INPUT)
return new UniswapTokenPriceFetcher([trade, route, pair, tok1, tok2])
}
getExecutionPrice6d = () =>
{
return this.trade.executionPrice.toSignificant(6);
}
getNextMidPrice6d = () =>
{
return this.trade.nextMidPrice.toSignificant(6);
}
}
module.exports = UniswapTokenPriceFetcher
Thank you everybody!
EDIT: I know Uniswap only pairs with WETH so one of my token variables is unneccesary, but the problem remains the same! Also keep in mind that I want to store an instance of this class for latter use inside another file.

Answer 1

You should either call the build function with await
const priceFetcher = await UniswapTokenPriceFetcher.build(token1, token2)
or followed by then
UniswapTokenPriceFetcher.build(token1, token2).then(priceFetcher => {...})
I don't see any other way.