Javascript - Error encountered when utilizing a for loop to insert a new column into an array

Question

Javascript - Error encountered when utilizing a for loop to insert a new column into an array

I have been utilizing an API to fetch data on various stocks, and I am attempting to include a column named "symbol" with the query values using the function insertColumn. However, I am encountering an error message that says

(node:15732) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'result' of undefined

. I have made an attempt at modifying let result to this.result and then executing insertColumn.call(this), but unfortunately, the same error persists. Initially, I assumed it could be related to a closure error, but now I'm uncertain.

import ObjectsToCsv from 'objects-to-csv';
import yahooFinance from 'yahoo-finance2';



async function api(){

  const query = 'TSLA';
  const queryOptions = { period1: '2021-08-06', interval: "1d"};
  let result = await yahooFinance.historical(query, queryOptions);

    function insertColumn() {
      for (var i = 0; i < this.result.length; i++) {
        this.result[i].push({symbol: query});
      }
    };
    insertColumn();

  console.log(result);

  (async () => {
    const csv = new ObjectsToCsv(result);
    await csv.toDisk('C:/Users/Rafael Oliveira/Desktop/teste/test.csv');
  })();
};
api();

The current output looks something like this:

[
  {
    date: 2021-08-06T00:00:00.000Z,
    open: 711.900024,
    high: 716.330017,
    low: 697.630005,
    close: 699.099976,
    adjClose: 699.099976,
    volume: 15576200
  },...

However, my desired outcome is as follows:

[
  {
    date: 2021-08-06T00:00:00.000Z,
    open: 711.900024,
    high: 716.330017,
    low: 697.630005,
    close: 699.099976,
    adjClose: 699.099976,
    volume: 15576200
    symbol: 'TSLA' //this value will vary based on changes in the query part
  },

javascript arrays for-loop

Answer 1

Answer №1

To enhance your code, it is recommended to utilize javascript's Array.prototype.map function to add a symbol to each item:

import ObjectsToCsv from 'objects-to-csv';
import yahooFinance from 'yahoo-finance2';

async function fetchData(){
  const query = 'TSLA';
  const queryOptions = { period1: '2021-08-06', interval: "1d" };
  const result = await yahooFinance.historical(query, queryOptions);
  const resultWithSymbol = result.map((item) => ({ ...item, symbol: query }));

  console.log(resultWithSymbol);

  (async () => {
    const csv = new ObjectsToCsv(resultWithSymbol);
    await csv.toDisk('C:/Users/Rafael Oliveira/Desktop/teste/test.csv');
  })();
};
fetchData();

Answer 2

To enhance your code, it is recommended to utilize javascript's Array.prototype.map function to add a symbol to each item:

import ObjectsToCsv from 'objects-to-csv';
import yahooFinance from 'yahoo-finance2';

async function fetchData(){
  const query = 'TSLA';
  const queryOptions = { period1: '2021-08-06', interval: "1d" };
  const result = await yahooFinance.historical(query, queryOptions);
  const resultWithSymbol = result.map((item) => ({ ...item, symbol: query }));

  console.log(resultWithSymbol);

  (async () => {
    const csv = new ObjectsToCsv(resultWithSymbol);
    await csv.toDisk('C:/Users/Rafael Oliveira/Desktop/teste/test.csv');
  })();
};
fetchData();

Javascript - Error encountered when utilizing a for loop to insert a new column into an array

Answer №1

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