Support multiple select fields in form submissions

example/forms.html

@@ -56,7 +56,7 @@
         <br />
 
         <label for="get-form-select">Select list:</label>
-        <select name="select" id="get-form-select">
+        <select multiple name="select" id="get-form-select">
           <option>
             Option 1
           </option>
@@ -119,7 +119,7 @@
         <br />
 
         <label for="post-form-select">Select list:</label>
-        <select name="select" id="post-form-select">
+        <select multiple name="select" id="post-form-select">
           <option>
             Option 1
           </option>

lib/proto/attach-form.js

@@ -32,15 +32,40 @@ var formAction = function(el, event) {
   event.preventDefault()
 
   for (var elementKey in el.elements) {
+    if (Number.isNaN(Number(elementKey))) {
+      continue;
+    }
+
     var element = el.elements[elementKey]
+    var tagName = element.tagName.toLowerCase()
     // jscs:disable disallowImplicitTypeConversion
-    if (!!element.name && element.attributes !== undefined && element.tagName.toLowerCase() !== "button") {
+    if (!!element.name && element.attributes !== undefined && tagName !== "button") {
+      var type = element.attributes.type
       // jscs:enable disallowImplicitTypeConversion
-      if ((!element.attributes.type || element.attributes.type.value !== "checkbox" && element.attributes.type.value !== "radio") || element.checked) {
-        options.requestOptions.requestParams.push({
-          name: encodeURIComponent(element.name),
-          value: encodeURIComponent(element.value)
-        })
+      if ((!type || type.value !== "checkbox" && type.value !== "radio") || element.checked) {
+        // Build array of values to submit
+        var values = []
+
+        if (tagName === "select") {
+          var opt
+
+          for (var i = 0; i < element.options.length; i++) {
+            opt = element.options[i]
+            if (opt.selected) {
+              values.push(opt.value || opt.text)
+            }
+          }
+        }
+        else {
+          values.push(element.value)
+        }
+
+        for (var j = 0; j < values.length; j++) {
+          options.requestOptions.requestParams.push({
+            name: encodeURIComponent(element.name),
+            value: encodeURIComponent(values[j])
+          })
+        }
       }
     }
   }