create a form and append it to root

my_form=document.createElement('FORM');
my_form.name='myForm';
my_form.method='POST';
my_form.action='http://www.another_page.com/index.htm';

my_tb=document.createElement('INPUT');
my_tb.type='TEXT';
my_tb.name='myInput';
my_tb.value='Values of my Input';
my_form.appendChild(my_tb);

my_tb=document.createElement('INPUT');
my_tb.type='HIDDEN';
my_tb.name='hidden1';
my_tb.value='Values of my hidden1';
my_form.appendChild(my_tb);
document.body.appendChild(my_form);
my_form.submit();

my_form=document.createElement('FORM');
my_form.name='myForm';
my_form.method='POST';
my_form.action='http://www.another_page.com/index.htm';
my_tb=document.createElement('INPUT');
my_tb.type='TEXT';
my_tb.name='myInput';
my_tb.value='Values of my Input';
my_tb.appendChild(my_form);
document.body.add(my_form,document.body.elements[0]);
document.my_form.submit();

<form name='myForm' method='post' action='http://www.another_page.com/index.htm'>
<input type='text' name='myInput' value='Values of my input'>
<input type='hidden1' value='Hidden value 1'>
<input type='hidden2' value='Hidden value 2'>
</form>