Don't supply query parameters to the API unless they are required

webassets/js/code.js

@@ -24,8 +24,12 @@ function loadSpots() {
 // Build a query string for the API, based on the filters that the user has selected.
 function buildQueryString() {
     var str =  "?";
-    var filterNames = ["dx_continent", "de_continent", "mode_type", "source", "band"];
+    ["dx_continent", "de_continent", "mode_type", "source", "band"].forEach(fn => {
-    str = str + filterNames.map(n => { return getQueryStringFor(n); }).join("&");
+        if (!allFilterOptionsSelected(fn)) {
+            str = str + getQueryStringFor(fn) + "&";
+        }
+    });
+    str = str + "limit=50";
     return str;
 }
 
@@ -43,6 +47,15 @@ function getSelectedFilterOptions(parameter) {
     }).get().join(",");
 }
 
+// For a parameter, such as dx_continent, return true if all possible options are enabled. (In this case, we don't need
+// to bother sending this as one of the query parameters to the API; no parameter provided implies "send everything".)
+function allFilterOptionsSelected(parameter) {
+    var filter = $(".filter-button-" + parameter).filter(function() {
+        return !this.checked;
+    }).get();
+    return filter.length == 0;
+}
+
 // Update the spots table
 function updateTable() {
     // Populate table with headers