String with underscore Javascript meaning

Question

I've seen in some places that strings are surrounded by _() like _('some string').

For example in a desktop program with these imports:

const Applet = imports.ui.applet;
const St = imports.gi.St;
const Gdk = imports.gi.Gdk;
const Gtk = imports.gi.Gtk;
const Keymap = Gdk.Keymap.get_default();
const Caribou = imports.gi.Caribou;
const PopupMenu = imports.ui.popupMenu;
const Lang = imports.lang;
const Gio = imports.gi.Gio;
const Main = imports.ui.main;
const MessageTray = imports.ui.messageTray;

What is the use of that function?

Could be the name of a callable. In python: http://stackoverflow.com/questions/20920956/python-what-does-an-underscore-before-parenthesis-do For translation — Andrew Li, Jun 24 '16 at 21:28
Without knowing the sites I would guess _ is a function like function _(text, ...) { return translate(text,...). In order to write out some localized text — lexx9999, Jun 24 '16 at 21:28
Usually this is a function defined as a translator for internationalization. It's very short because it's used a lot. — Xedecimal, Jun 24 '16 at 21:28

Slava Knyazev · Answer 1 · 2016-06-24T21:36:50.060

6

It can really be anything. For instance the entire underscore library is built around using _ as a normal variable/function/class name.

_ is not a reserved character, not any more than i, a and so on.

Practical example:

_('test')
//ReferenceError: _ is not defined

function _(str){
    console.log(str);
}

_('test')
//Output: test

More often than not, if not using underscore.js, it would be used for a function that you would use very often hence only using a single character.

Note: As stated by @Xedecimal and @AliTorabi, it is also often used to name a function defined as a translator for internationalization since once again, it is very short and used a very often.

edited Jun 24 '16 at 21:36

answered Jun 24 '16 at 21:30

Slava Knyazev

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You could note the use of it with translation and globalization :) – Andrew Li Jun 24 '16 at 21:33
@AndrewL. No trouble. Otherwise edit to your liking. – Slava Knyazev Jun 24 '16 at 21:37
1

Very nice answer regardless – Andrew Li Jun 24 '16 at 21:37
Function declarations *hoist*, though, so the first `_('test')` in the practical example wouldn't cause errors at all. – noppa Jun 24 '16 at 21:42
@noppa Mmm.. sorry for not being clear I guess. But this is not one file being executed but a list of commands to run in say, a javascript console in order. – Slava Knyazev Jun 24 '16 at 21:46
Yeah I guess that was nitpicking anyways, the meat of the answer is correct regardless of the example. – noppa Jun 24 '16 at 21:49

score 0 · Answer 2 · answered Jun 24 '16 at 22:54

0

The is NO _ function in JavaScript, unless you implement it your self, or use an external library.

const _ = (str) => str.split('').join('_')
_("hello") // "h_e_l_l_o"

answered Jun 24 '16 at 22:54

webdeb

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score 0 · Accepted Answer · answered Oct 02 '16 at 11:10

I'll answer myself based on comments I got. (I already knew _ is not anything special but a normal function name, that wasn't the question).

Based on those imports, it seems to be part of a system library. Concretely this:

const Lang = imports.lang;

It is used to translate strings into other languages automatically. For example:

_('Hello') //Hola

String with underscore Javascript meaning

3 Answers3