Liferay provides a very useful text localization method, which can be used with LanguageUtil Java class (and its counterpart class UnicodeLanguageUtil) or with <liferay-ui:message/> taglib.

But how can we use the same method with Javascript? Let's see!

Let's suppose to have created a Liferay plugin, with the usual translation property file Language.properties and the following items:

sample-text=Sample text
sample-text-with-param-x=Sample text with param: {0}

As we said above, it's possibile to display translated messages with taglib:

<liferay-ui:message key="sample-text" />
<liferay-ui:message key="sample-text-with-param-x" arguments='<%=new String[] { "Foo" }%>' />

Or with Java class:

LanguageUtil.get(pageContext, "sample-text");
LanguageUtil.format(pageContext, "sample-text-with-param-x", new String[] {"Foo"});

Both methods above will produce the same output:

Sample text
Sample text with param: Foo

But if we need a translation in a Javascript function, how can we do? Fortunately there's the not so well documented Liferay provided library and especially the Javascript object Liferay.Language.

With this Javascript object, we can use the localization method in this way:

alert(Liferay.Language.get('sample-text'));
alert(Liferay.Language.get('sample-text-with-param-x', ['Foo']));

But there's only a limitation in Javascript localization method: Liferay.Language object searchs the translation in the portal scope and not in the portlet scope.

So every message we need to use with Javascript, must be define with a language hook.