So I'm trying to use the Drupal.t() function in some of my custom Javascript code (in my theme).
How do I get the strings I need populated in the Drupal.locale.strings object? I see some strings in there, but of course the entire database can't be loaded. What's the best way to add to it? I would like to use the PHP t() function so that the strings added can be edited in the Translate interface.
Drupal handles populating the needing strings into the javascript object. Much like the entire collection of strings isn't loaded on every page, only the needed strings are added to the JavaScript.
I believe this is done by traversing the script files before they are actually added to the page.
So if you add Drupal.t('Some string'); to your JavaScript code, you should be able to translate that in the translate interface.
Just ran into this same issue today and researched it a bit more. Chris above has a good comment, but it's ultimately incorrect. You do not need to use Drupal.behaviors for it to work.
As noted by JonMcL himself in his last comment, the function _locale_parse_js_file in locale.inc is responsible for the parsing of Drupal.t("somestring") patterns starting from row 1493 (in Drupal 7.22):
preg_match_all('~
[^\w]Drupal\s*\.\s*t\s* # match "Drupal.t" with whitespace
\(\s* # match "(" argument list start
(' . LOCALE_JS_STRING . ')\s* # capture string argument
(?:,\s*' . LOCALE_JS_OBJECT . '\s* # optionally capture str args
(?:,\s*' . LOCALE_JS_OBJECT_CONTEXT . '\s*) # optionally capture context
?)? # close optional args
[,\)] # match ")" or "," to finish
~sx', $file, $t_matches);
It's just a "dumb" parsing function that doesn't care about semantics and simply finds all instances of Drupal.t("something") in any file it receives.
What could be a common gotcha is that you need to have the whole string in your source code in the Drupal.t("translateme") form, because (obviously) no javascript gets executed when the file is opened through file_get_contents in php. That means you can never do Drupal.t(somevariable) and hope Drupal will catch all string-containing javascript variables that you throw at Drupal.t.
If you want to translate "women" for a chart and give the string a context, the syntax would be:
Drupal.t("women", {}, {context: "charts"}
Also, if you have drush installed, verify your js file is parsed with the command;
drush vget javascript_parsed
Then you can clean your cache with
drush cc all
... and repeat the vget command above to verify the list of already parsed files is empty. This way your file will get reparsed next run (verify that too).
drush vget javascript_parsed! A quicker way to force rebuild translations script files is by just removing CSS and JS files using drush @sitealias cc css-js.
Couple gotchas I've run into while implementing multilingual JS in Drupal 7:
First, make sure your JS file is not being included inline. As of Drupal 7.22, Drupal.locale.strings doesn't seem to automatically update itself if you're inlining JavaScript files in Drupal. The translation interface still picked up the string anyway, adding to my confusion.
Second, make sure you're using Drupal.behaviors to attach your JS to the page. Regular JS closures will not trigger Drupal's "magic" parsing of Drupal.t() invocations. This is technically something you should be doing anyway ;)
From there it really is pretty painless. Just use Drupal.t() around text you want translated, clear your cache each time you update the file, and your translators should see the new string in the interface at /admin/config/regional/translate/translate. It's quite nice once you get it working.
