How to convert a function from Visual Studio to a regular JS function?

In the visual full 0, so forgive. There is a button that performs this function when clicked.

onclick="javascript:WebForm_DoPostBackWithOptions(new WebForm_PostBackOptions("ctl00$cphMain$btnSave", "", true, "", "", false, false))" 

how to convert it into a regular js function like:

  function save() { выполнить эту функцию }