<!DOCTYPE html><html><body><form id="frm1" action="form_action.asp">First name: <input type="text" name="fname" value="Donald"><br>Last name: <input type="text" name="lname" value="Duck"><br><input type="submit" value="Submit"></form><p>The number of elements in "frm1" are:<script>document.write(document.getElementById("frm1").length);</script></p></body></html>希望本文所述对大家的javascript程序设计有所帮助。