BF: Replace 'use prefs' default with 'height' for JS window units

'use preferences' for window units breaks JS code. This fix sets the default window units as 'height'. Fixes new issue in #2227.

psychopy/experiment/components/settings/__init__.py

@@ -723,17 +723,25 @@ def writeWindowCode(self, buff):
         buff.writeIndentedLines(code)
 
     def writeWindowCodeJS(self, buff):
+        """Setup the JS window code.
+        """
+        # Replace instances of 'use prefs'
+        units = self.params['Units'].val
+        if units == 'use prefs':
+            units = 'height'
+
         code = ("// init psychoJS:\n"
-        "var psychoJS = new PsychoJS({{\n"
-        "  debug: true\n"
-        "}});\n\n"
-        "// open window:\n"
-        "psychoJS.openWindow({{\n"
-        "  fullscr: {fullScr},\n"
-        "  color: new util.Color({params[color]}),\n"
-        "  units: {params[Units]}\n"
-        "}});\n").format(fullScr=str(self.params['Full-screen window']).lower(),
-            params=self.params)
+                "var psychoJS = new PsychoJS({{\n"
+                "  debug: true\n"
+                "}});\n\n"
+                "// open window:\n"
+                "psychoJS.openWindow({{\n"
+                "  fullscr: {fullScr},\n"
+                "  color: new util.Color({params[color]}),\n"
+                "  units: '{units}'\n"
+                "}});\n").format(fullScr=str(self.params['Full-screen window']).lower(),
+                                 params=self.params,
+                                 units=units)
         buff.writeIndentedLines(code)
 
     def writeEndCode(self, buff):