Issue 4993 - Add operator-linebreak rule to our JavaScript style guide

pages/coding-style.html

Index: pages/coding-style.html
diff --git a/pages/coding-style.html b/pages/coding-style.html
index a2791736e26db9a375cbcc7185985d1fa73ebaee..56fd9bbf46973711e2b2473e7e1fd78812c30e61 100644
--- a/pages/coding-style.html
+++ b/pages/coding-style.html
@@ -25,6 +25,7 @@ title=Coding Style
 <ul>
   <li>{{s15 Follow the Mozilla Coding Style's <a href="https://developer.mozilla.org/en-US/docs/Developer_Guide/Coding_Style#JavaScript_practices">JavaScript practices</a>.}}</li>
   <li>{{javascript-strict Always use <a href="https://developer.mozilla.org/docs/Web/JavaScript/Reference/Strict_mode">strict mode</a>.}}</li>
+  <li>{{javascript-operator-linebreak When splitting overlong expressions into multiple lines the joining binary operators should be left at the end of the line, before the linebreak. The exception being member access operators, such as <code><fix>.</fix></code> which should be placed on the following line.}}</li>

[Wladimir Palant, 2017/03/17 13:49:25]

I don't feel comfortable advising you about English, but "being" in the last
sentence sounds wrong, this being a sentence of its own. Maybe "The exception
are member access operators"? Also, I think that there should be a comma before
"which."

[kzar, 2017/03/17 14:56:33]

You should, your English is much better than mine :p
I've had another go, what do you think?
Yea, I thought that too, but it was kind of confusing having the comma right
after the period. To me at least it looked like the operator we were talking
about was ".,". I couldn't see another way to reorder the sentence to avoid
that, but I'm open to suggestions.

   <li>{{javascript-if-else-braces When an <code><fix>if</fix></code> statement, an <code><fix>else</fix></code> statement or a loop spans over more than one line always enclose it with braces.}}</li>
   <li>{{s18 In classes, prefix private functions with a single underscore to make them pseudo-private.}}</li>
   <li>{{javascript-spacing-literals Don't add any spaces immediately after opening, or before closing, an object or array literal.}}</li>