ANGULAR 5 : how to export data to csv file

I am beginner in angular and I am working on Angular 5, Node v8.11.3.

I want to realize a generic function that takes in parameter data and headers. And as output a csv file.

I create a component called ' FactureComponent ' Then I generate a service called ' DataService ' then I create a getFactures function that retrieves a list of my items from a mock and it works very well.

import { Component, OnInit } from '@angular/core';
import { DataService } from '../data.service';
import { FACTURES } from '../mock.factures';

@Component({
selector: 'app-facture',
templateUrl: './facture.component.html',
styleUrls: ['./facture.component.scss']
})
export class FactureComponent implements OnInit {

factures = [];
columns  = ["Id","Reference","Quantite","Prix Unitaire"];
btnText:  String = "Export CSV";

constructor(private _data: DataService) { }

ngOnInit() {
this.getFactures();
}
getFactures(){
this.factures=this._data.getFactures();
}
generateCSV(){
console.log("generate");
}
}

you will find below the view

<form>
<input type="submit" [value]="btnText" (click)="generateCSV()"/>
</form>

<table>
 <tr>
   <th *ngFor="let col of columns">
      {{col}}
   </th>
 </tr>
 <tr *ngFor="let facture of factures">
  <td>{{facture.id}}</td>     
  <td>{{facture.ref}}</td>
  <td>{{facture.quantite}}</td>
  <td>{{facture.prixUnitaire}}</td>
 </tr>
</table>

So I want to realize a function that converts my data displayed on the view into a csv file.

Update: Here is slightly better way to do it:

1. Open up command prompt in the directory of your project.
2. Install file-saver by typing npm install --save file-saver
3. import { saveAs } from 'file-saver'; into your .ts file.
4. Here is the updated code based on the new import.

downloadFile(data: any) {
    const replacer = (key, value) => value === null ? '' : value; // specify how you want to handle null values here
    const header = Object.keys(data[0]);
    let csv = data.map(row => header.map(fieldName => JSON.stringify(row[fieldName], replacer)).join(','));
    csv.unshift(header.join(','));
    let csvArray = csv.join('\r\n');

    var blob = new Blob([csvArray], {type: 'text/csv' })
    saveAs(blob, "myFile.csv");
}

Credits to this answer for converting an object to CSV.

Here is the method to use:

downloadFile(data: any) {
  const replacer = (key, value) => (value === null ? '' : value); // specify how you want to handle null values here
  const header = Object.keys(data[0]);
  const csv = data.map((row) =>
    header
      .map((fieldName) => JSON.stringify(row[fieldName], replacer))
      .join(',')
  );
  csv.unshift(header.join(','));
  const csvArray = csv.join('\r\n');

  const a = document.createElement('a');
  const blob = new Blob([csvArray], { type: 'text/csv' });
  const url = window.URL.createObjectURL(blob);

  a.href = url;
  a.download = 'myFile.csv';
  a.click();
  window.URL.revokeObjectURL(url);
  a.remove();
}

I'll add on later if I found a better way to do it.