function to generate values of a javascript object

Question

The following code works but I am wondering if it can be improved both readability and performance.
I am using jquery and underscore.
Any suggestions, comments or feedbacks will be appreciate. thanks.

var getThemeName = function (theme_name, transparency) {
 if (theme_name === 'light') {
 if (transparency) {
 return translator.get('messages:theme.info.light_with_transparency', {
 percentage: transparency
 });
 }
 return translator.get('messages:theme.info.light');
 } else if (theme_name === 'dark') {
 if (transparency) {
 return translator.get('messages:theme.info.dark_with_transparency', {
 percentage: transparency
 });
 }
 return translator.get('messages:theme.info.dark');
 }
};
var THEME_ITEMS = {
 themeLight: getThemeName('light'),
 themeLightTransparency75: getThemeName('light', 75),
 themeLightTransparency50: getThemeName('light', 50),
 themeLightTransparency25: getThemeName('light', 25),
 themeDark: getThemeName('dark'),
 themeDarkTransparency75: getThemeName('dark', 75),
 themeDarkTransparency50: getThemeName('dark', 50),
 themeDarkTransparency25: getThemeName('dark', 25)
};

Answer 1

If you keep the naming consistent, you could probably do something like:

function getThemeName(themeName, transparency) {
 var name = "messages:theme.info." + themeName;
 if( transparency ) {
 name += "_with_transparency";
 return translator.get(name, { percentage: transparency });
 } else {
 return translator.get(name);
 }
}