They are obviously talking about in generalities.
That doesn't mean everyone is doing it. Or that it fits every task.
Here is some random survey from 2012 as an example:
58.9% Javascript
58.9% sql
51.1% jquery
37.6% java
37.6% c#
28.9% php
23.4% python
21.1% c++
The year after:
57.9% Javascript
53% sql
37.9% java
37.6% c#
26.2% php
22.5% python
21.7% c++
18% c
10.3% objective-c
9.8% node.js
9.1% ruby
http://blog.stackoverflow.com/...
I don't know how representative Stack Overflow is or what it means, I just know Javascript is used a lot.
If that means they are using Javascript only on the website front-end or also for other things. Who knows.
Node.js is listed as 'most exciting new technologies':
38.4% node.js
36.1% arduino /raspberry pi
28.4% angular js
So maybe it's used on the server too.