Saving data from a function to a global variable

Question

In the code below I'm saving the data I get from a stock API to newData and then I want to pass this newData to data which is supposed to be a global variable as an array. The main goal is to then save this array as CSV, but I first need to get the array

const yahooStockAPI  = require('yahoo-stock-api');

let data = [];

async function main() {
    const startDate = new Date('07/01/2021');
    const endDate = new Date('07/25/2021');
    const newData = await yahooStockAPI.getHistoricalPrices(startDate, endDate, 'AAPL', '1d');
    data = newData

};
console.log(data);

When I print data, I get back [ ] an empty array. Shouldn't it retrieve the data from the API instead? I've searched other questions like this in stackoverflow and tried to implement some of the fixes, but none seem to be working

For reference, this is the ouput I get from the await yahooStockAPI.getHistoricalPrices(startDate, endDate, 'AAPL', '1d'); line of code

{
  error: false,
  currency: 'USD',
  response: [
    {
      date: 1627047000,
      open: 147.5500030517578,
      high: 148.72000122070312,
      low: 146.9199981689453,
      close: 148.55999755859375,
      volume: 71447400,
      adjclose: 148.33775329589844
    },
    {
      date: 1626960600,
      open: 145.94000244140625,
      high: 148.1999969482422,
      low: 145.80999755859375,
      close: 146.8000030517578,
      volume: 77338200,
      adjclose: 146.58038330078125
    },...

This is the data I want to save in the global variable data array

Thank you in advance

Don't save data from an async function into a global variable. — evolutionxbox
– evolutionxbox, Commented Aug 9, 2021 at 11:00
Does this answer your question? How to return the response from an asynchronous call — evolutionxbox
– evolutionxbox, Commented Aug 9, 2021 at 11:01
So we can't save data from an async function as an array to a global variable? I've removed the async function, but I keep getting an empty array. I appreciate your answer though — user139442
– user139442, Commented Aug 9, 2021 at 11:05
You can, but you won't want to. There's no reliable way to make sure the variable is up-to-date or even defined. You'd likely run into race conditions — evolutionxbox
– evolutionxbox, Commented Aug 9, 2021 at 11:07
Removing the async function I get as output Promise { <pending> } and I no longer get the values back — user139442
– user139442, Commented Aug 9, 2021 at 11:17

sschwei1 · Accepted Answer · 2021-08-09 11:39:57Z

1

The problem is your main function is never called, so there will never be stored a value in your data variable, you need to explicitly call your main function

I assume you mix some things up with c/c++?

const yahooStockAPI  = require('yahoo-stock-api');

let data = [];

async function main() {
    const startDate = new Date('07/01/2021');
    const endDate = new Date('07/25/2021');
    const newData = await yahooStockAPI.getHistoricalPrices(startDate, endDate, 'AAPL', '1d');
    data = newData

};

// call your main function
await main();

console.log(data);

Edit after comment from @evolutionxbox

Using top-level await will only work inside modules and should only be used in certain situations

Here are some resources you can take a look at:

edited Aug 9, 2021 at 11:39

answered Aug 9, 2021 at 11:08

sschwei1

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2 Comments

evolutionxbox Over a year ago

stackoverflow.com/questions/46515764/… please note that using await at the top level is only allowed in certain places

sschwei1 Over a year ago

@evolutionxbox Thanks a lot, I just tried it in a playground and it worked, I didn't even know this was a thing, gonna read a bit into it and update my answer

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