javascript - go on first page not working -

i'm trying create button go on first history page don't know why doesn't code work.this code:

function firstpg() {    var startpt = '-' + window.history.length;    window.history.go(startpt);  }

<!doctype html>  <html>    <head>    </head>    <body>      <button onclick="firstpg()">go first</button>    </body>  </html>

what problem?

the history includes current page need decrement 1 length in order go first page.

var startpt = '-' + ( window.history.length - 1) ;

var startpt = -(window.history.length - 1) ;

QR