Use espeak_SetVoiceByName in emscripten glue when only name is provided.

emscripten/espeakng_glue.cpp

     espeak_SetSynthCallback(NULL);
   }
 
-  void set_voice(
+  long set_voice(
         const char* aName,
-        const char* aLang,
+        const char* aLang=NULL,
         unsigned char aGender=0,
         unsigned char aAge=0,
         unsigned char aVariant = 0
     ) {
-    espeak_VOICE props = { 0 };
-    props.name = aName;
-    props.languages = aLang;
-    props.gender = aGender;
-    props.age = aAge;
-    props.variant = aVariant;
+    long result = 0;
+    if (aLang || aGender || aAge || aVariant) {
+      espeak_VOICE props = { 0 };
+      props.name = aName;
+      props.languages = aLang;
+      props.gender = aGender;
+      props.age = aAge;
+      props.variant = aVariant;
+      result = espeak_SetVoiceByProperties(&props);
+    } else {
+      result = espeak_SetVoiceByName(aName);
+    }
+
     // This way we don't need to allocate the name/lang strings to the heap.
     // Instead, we store the actual global voice.
-    espeak_SetVoiceByProperties(&props);
     current_voice = espeak_GetCurrentVoice();
+
+    return result;
   }
 
   int getSizeOfEventStruct_() {

emscripten/espeakng_glue.idl

   void eSpeakNGWorker();
   void synth_(DOMString aText, VoidPtr aCallback);
   long getSizeOfEventStruct_();
-  void set_voice(DOMString aName, DOMString aLang, optional octet gender=0, optional octet age=0, optional octet aVariant=0);
+  long set_voice(DOMString aName, DOMString aLang, optional octet gender=0, optional octet age=0, optional octet aVariant=0);
   [Const] attribute espeak_VOICE[] voices;
   readonly attribute long samplerate;
   attribute long rate;

emscripten/js/demo.js

   tts.set_pitch(Number(document.getElementById('pitch').value));
   console.log('  Setting pitch... done');
   console.log('  Setting voice...');
-  tts.set_voice.apply(tts, (document.getElementById('voice').value.split(',')));
+  tts.set_voice(document.getElementById('voice').value);
   console.log('  Setting voice... done');
 
   var now = Date.now();
           var sel = document.getElementById('voice');
           var index = 0;
           for (voice of result) {
-            for (lang of voice.languages) {
-              var opt = document.createElement('option');
-              opt.text = voice.name + ' (' + lang.name + ')';
-              opt.value = [voice.name, lang.name];
-              console.log('Adding voice: ' + opt.text);
-              sel.add(opt);
-              if (voice.name === 'default') {
-                opt.id = 'default-voice';
-                opt.selected = true;
-              }
+            var opt = document.createElement('option');
+            var languages = voice.languages.map(function(lang) {
+              return lang.name;
+            }).join(", ");
+            opt.text = voice.name + ' (' + languages + ')';
+            opt.value = voice.identifier;
+            console.log('Adding voice: ' + opt.text);
+            sel.add(opt);
+            if (voice.name === 'default') {
+              opt.id = 'default-voice';
+              opt.selected = true;
             }
           }
           console.log('Leaving cb2');