How to create a dialog with “yes” and “no” options?

You’re probably looking for confirm(), which displays a prompt and returns true or false based on what the user decided:

if (confirm('Are you sure you want to save this thing into the database?')) {
  // Save it!
  console.log('Thing was saved to the database.');
} else {
  // Do nothing!
  console.log('Thing was not saved to the database.');
}

var answer = window.confirm("Save data?");
if (answer) {
    //some code
}
else {
    //some code
}

Use window.confirm instead of alert. This is the easiest way to achieve that functionality.

How to do this using 'inline' JavaScript:

<form action="http://www.google.com/search">
  <input type="text" name="q" />
  <input type="submit" value="Go"
    onclick="return confirm('Are you sure you want to search Google?')"
  />
</form>