Launch download in the same tab without opening new tab or window in Javascript

HTML5 solution with 'download' attribute

<a href="/images/myw3schoolsimage.jpg" download>

https://www.w3schools.com/tags/att_a_download.asp

function startDownload(url) {

    window.location.href = url;
}

This will start the download in the same page, exactly like when you click a link without any target other than _self.

To force the download of a file, make sure you send the right headers with it:

Content-Disposition: attachment; filename="mypdf.pdf";

This will make sure that the file is not displayed in the browser instead of being downloaded. Replace the filename part with the filename you want as default on the save as dialog.

window.open will open a new window \ tab (depending on user preferences) ... to just download the file use

window.location.href = url;

You can use this if the url returns a downloadable file rather than a web page