Let me try to explain to you what you did and what you need to do to make your code work in the way you intended.

<script>

$('#wpsl-search-button1') // jQuery method to retrieve an element with the ID wpsl-search-button1

   .click(function() { // Attach a click listener to the element

       var url = '/pages/location-search/?'; // Declare a variable with the name url containing a string /pages/location-search/?

       $('#wpsl-search-input1') // retrieving the element with the id wpsl-search-input1

           .each(function() { // looping over all elements found by the id selector (ID's are unique, so the query above should always return one jQuery element. No need for a loop here)

               url += 'zip=' + $(this).val() + &; // append a zip parameter with the value of the found element (this is refering to the current element of the iteration -> the input)

           });

       window.location.replace(url); // replace the current resource with the one in the url variable

});

</script>

If you just want to redirect to a url based by the input value use this code:

<script>

$('#wpsl-search-button1').click(function() { // you dont need the .each, because you are selecting by id

   var inputURL = $('#wpsl-search-input1').val();

   window.location.href = `/pages/location-search/?zip=${inputURL}`; // Redirecting to the passed url (also working relative to the current URL)

   return false; // Cheap way to call the event.preventDefault() method

});

</script>