Javascript checkbox multipule post

i have this form. I need the input tag email post to a standrard direction www.loc.com/standard and if checkbox checked then email input tag post also to specific direcxtion for example www.loc.com/dir1. Also if user select 2 checkboxes also send to both this directions including the standard one.

Thank you

Here is my code (but it doesn't work properly):

<form id="ms-sub-form" method="post" action="http://ift.tt/1JNVZC1">
<input type="text" name="ms-email" id="email" size="30" style="border:1px solid #ffffff; height: 30px" placeholder="Email" />

<input type="checkbox" name="operation[0]" onclick="if(this.checked){form.action = 'www.loc.com/dir1'};">CheckBox1

            <input type="checkbox" name="operation[1]" onclick="if(this.checked){form.action = 'www.loc.com/dir2'};">CheckBox2

            <input type="checkbox" name="operation[2]" onclick="if(this.checked){form.action = 'www.loc.com/dir3'};">CheckBox3
   <p>
   <input type="submit" name="submit" value="sign">
   </p>
</form>