Submit POST request

I’m currently hacking my way through a Shopify theme. There is a form like this:

  <form action="/cart" method="post">
      <button  type="submit">Checkout</button>

When this button is clicked you are taken to the checkout page. Fairly standard.
However, I want to display a popup before the form action is completed. Not a browser API alert box something I can style and have control over in the browser.

So I’ve updated the form and added some JavaScript:

  <form action="/cart" method="post">
      <button  onclick="confirmTerms(event)">Checkout</button>

  const confirmTerms = (event) => {
     // confirmTerms shows a popup box with an accept and deny buttons and stops the event from firing.
    document.getElementsByClassName('background-cover')[0].style = "display: flex; opacity: 1";

  const termsAccept = () => {
    //terms accept is connected to the acceptance button on the form that is displayed by confirmTerms.

    const form = document.getElementById("chart-checkout-form");
    form.submit() // <- this is the specific method that I'm trying to work through I've tried all the iterations listed below.


Based on the user’s choice in the popup, I want to then submit the POST request and be directed to the checkout page.

So what is need is something with the functionality of form.requestSubmit but that works with all major browsers (including Safari which requestSubmit does not). Any ideas of something that will let me do what requestSubmit does?

That’s my question in a nutshell, for further context feel free to read the rest of the post:

First I reached for:


But this took me to /cart rather than /checkout which I assume is because the form’s action is cart and it’s not taking into account the method="post".

So then I tried:

    const xhttp = new XMLHttpRequest();"POST", "/cart", false);

No errors, but when the button is hit nothing happens. Lastly, I tried an async function with fetch and had the same issue as xhttp.

The only thing I have gotten to work is form.requestSubmit but that is not supported by Safari so it’s a no go. But that’s what I need, essentially the same functionality one gets from form.requestSubmit.

Where did you use it ?

Ah sorry that was a typo, I didn’t copy and paste my form button so I wrote the wrong function call, I have updated this to show the original confirmTerms function and a function for accepting terms.

If your popup html is inside your form you can use a standard button for this. Add the type="button" attribute to your initial “Checkout” button, this will prevent the form being submitted.

Then inside your popup html ensure you have a button, by default it will act like a submit button as long as it’s within your form. You can optionally give it an attribute of type="submit".

As an aside, if you need to conditionally change the forms action attribute, you can do this by setting a formaction attribute on a button. e.g.

<button formaction="/checkout">Accept Terms</button>

I’ve put together a working example here:

As a final note from a UX perspective, I’d advocate adding a checkbox in your form instead of using a popup like this. It’s a much less invasive approach for your end user, and more accessible. If you make it a required field you can also prevent the form being submitted without the need for javascript.

The popup html is not inside the form, it’s located elsewhere on the page. In theory it could be but since the form is nested several child elements deep and nestled off to the right side of the screen.

Although I just swapped some things around, and put the popup with the submit button inside the form. It’s still not working so I’m wondering if there is something that Shopify is doing that I’m missing.

Ended up solving this by just moving the location of the form to the confirmation box rather than the “checkout” button.