How to open a new window on form submit

Question

No need for Javascript, you just have to add a target="_blank" attribute in your form tag.

<form target="_blank" action="http://example.com"
      method="post" id="mc-embedded-subscribe-form"
      name="mc-embedded-subscribe-form" class="validate"
>

In a web-based database application that uses a pop-up window to display print-outs of database data, this worked well enough for our needs (tested in Chrome 48):

<form method="post" 
      target="print_popup" 
      action="/myFormProcessorInNewWindow.aspx"
      onsubmit="window.open('about:blank','print_popup','width=1000,height=800');">

The trick is to match the target attribute on the <form> tag with the second argument in the window.open call in the onsubmit handler.

For a similar effect to form's target attribute, you can also use the formtarget attribute of input[type="submit]" or button[type="submit"].

From MDN:

...this attribute is a name or keyword indicating where to display the response that is received after submitting the form. This is a name of, or keyword for, a browsing context (for example, tab, window, or inline frame). If this attribute is specified, it overrides the target attribute of the elements's form owner. The following keywords have special meanings:

• _self: Load the response into the same browsing context as the current one. This value is the default if the attribute is not specified.
• _blank: Load the response into a new unnamed browsing context.
• _parent: Load the response into the parent browsing context of the current one. If there is no parent, this option behaves the same way as _self.
• _top: Load the response into the top-level browsing context (that is, the browsing context that is an ancestor of the current one, and has no parent). If there is no parent, this option behaves the same way as _self.

onclick may not be the best event to attach that action to. Anytime anyone clicks anywhere in the form, it will open the window.

<form action="..." ...
    onsubmit="window.open('google.html', '_blank', 'scrollbars=no,menubar=no,height=600,width=800,resizable=yes,toolbar=no,status=no');return true;">