How to save a file to my desktop folder angular 6

Specifying download location dialog is completely browser dependent. Through Javascript, you cannot specify a user's Desktop location to download files. Javascript accessing your directory locations will cause serious security risks. At max, you can change your browser settings to ask for the download location every time.

To implement a normal download at default download location, you can use filesaver

Just import it in your code as:

import { saveAs } from 'file-saver'

and use saveAs in your downloadUrlToFile method.

dataURLtoFile(dataurl, filename, format) {
    const arr = dataurl.split(',');
    const mime = arr[0].match(/:(.*?);/)[1];
    const bstr = atob(arr[1]);
    let n = bstr.length;
    const u8arr = new Uint8Array(n);
    while (n--) {
        u8arr[n] = bstr.charCodeAt(n);
    }
    saveAs(new File([u8arr], filename, {type: format}));
}

See an example here: https://stackblitz.com/edit/angular-xrubur?file=src%2Fapp%2Fapp.component.ts

you can try function below. IT works on both IE10+ and other evergreen compatible browsers

 createImageFromBlob(image: Blob) {
    if (window.navigator.msSaveOrOpenBlob) // IE10+
      window.navigator.msSaveOrOpenBlob(image, "myFile.jpg");
    else {
      var url = window.URL.createObjectURL(image);
      window.open(url);
    }
  }

There is no need for an external library for triggering the "Save as..." window (such as file-saver, which is different from the node filesaver mentioned in another answer in here, meant for another purpose).

The simplest way I found was to create an <a> element in one of the component's methods:

saveAFile(): void {
  const dlink: HTMLAnchorElement = document.createElement('a');
  dlink.download = 'myfile.txt'; // the file name
  const myFileContent: string = 'I am a text file! 😂';
  dlink.href = 'data:text/plain;charset=UTF-8,' + myFileContent;
  dlink.click(); // this will trigger the dialog window
  dlink.remove();
}

Which can be invoked with a click event in the template, for example:

<button (click)="saveAFile()">Save file</button>

I also initially transformed the file's contents into a Blob but I soon noticed that even with the right charset, complex characters may be lost in translation (e.g. 😂).

You might also find useful the complete list of media/MIME types for creating non-plain text files (e.g. text/csv or application/json).