When a user submits an HTML form, for example by clicking the submit button, the browser makes an HTTP request to send the data in the form. But instead of this declarative approach, Web apps sometimes use JavaScript APIs such as fetch() to send data programmatically to an endpoint that expects a form submission. This article explains why this is an important use case and how to do it....of this declarative approach, web apps sometimes use JavaScript...However, many web apps, especially progressive web apps and single-page...