<s>
Isomorphic	B-Language
JavaScript	I-Language
,	O
also	O
known	O
as	O
Universal	B-Language
JavaScript	I-Language
,	O
describes	O
JavaScript	B-Language
applications	O
which	O
run	O
both	O
on	O
the	O
client	B-Protocol
and	O
the	O
server	B-Application
.	O
</s>
<s>
Isomorphic	B-Language
JavaScript	I-Language
works	O
in	O
the	O
context	O
of	O
a	O
single-page	B-Application
application	I-Application
(	O
SPA	O
)	O
.	O
</s>
<s>
In	O
a	O
typical	O
SPA	O
,	O
most	O
of	O
the	O
application	O
logic	O
,	O
including	O
routing	O
,	O
is	O
encapsulated	O
in	O
a	O
bundled	O
JavaScript	B-Language
file	O
that	O
is	O
sent	O
to	O
the	O
client	B-Protocol
.	O
</s>
<s>
While	O
this	O
frees	O
up	O
the	O
server	B-Application
,	O
as	O
it	O
does	O
not	O
have	O
to	O
handle	O
so	O
many	O
requests	O
,	O
it	O
also	O
makes	O
the	O
initial	O
load	O
slow	O
for	O
the	O
client	B-Protocol
,	O
as	O
the	O
entire	O
application	O
needs	O
to	O
be	O
sent	O
over	O
to	O
the	O
client	B-Protocol
.	O
</s>
<s>
With	O
Isomorphic	B-Language
JavaScript	I-Language
,	O
when	O
a	O
client	B-Protocol
web	O
page	O
is	O
first	O
requested	O
from	O
the	O
server	B-Application
,	O
the	O
view	O
of	O
the	O
page	O
is	O
generated	O
on	O
the	O
server	B-Application
,	O
similar	O
to	O
server-side	O
dynamic	O
web	O
pages	O
,	O
and	O
sent	O
over	O
to	O
the	O
client	B-Protocol
.	O
</s>
<s>
The	O
client	B-Protocol
can	O
then	O
render	O
the	O
view	O
immediately	O
.	O
</s>
<s>
After	O
the	O
initial	O
view	O
is	O
rendered	O
,	O
the	O
complete	O
SPA	O
is	O
downloaded	O
in	O
the	O
background	O
,	O
and	O
subsequent	O
actions	O
are	O
handled	O
client-side	O
.	O
</s>
<s>
The	O
naming	O
of	O
the	O
term	O
'	O
Isomorphic	B-Language
JavaScript	I-Language
 '	O
has	O
been	O
a	O
matter	O
of	O
controversy	O
.	O
</s>
<s>
However	O
,	O
others	O
have	O
proposed	O
to	O
use	O
the	O
term	O
Universal	B-Language
JavaScript	I-Language
instead	O
.	O
</s>
<s>
Better	O
user	O
experience	O
:	O
By	O
rendering	O
important	O
parts	O
of	O
the	O
application	O
with	O
the	O
real	O
data	O
on	O
the	O
server-side	O
,	O
an	O
isomorphic	O
application	O
can	O
show	O
a	O
meaningful	O
initial	O
page	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
client	B-Protocol
rendering	O
application	O
ca	O
n’t	O
show	O
any	O
meaningful	O
information	O
until	O
it	O
fetches	O
all	O
external	O
data	O
it	O
needs	O
.	O
</s>
<s>
Faster	O
overall	O
loading	O
time	O
:	O
Although	O
an	O
isomorphic	O
application	O
will	O
be	O
slower	O
in	O
responding	O
an	O
initial	O
page	O
compared	O
to	O
a	O
client	B-Protocol
rendering	O
application	O
(	O
as	O
it	O
fetches	O
data	O
and	O
renders	O
more	O
markups	O
on	O
the	O
server-side	O
before	O
responding	O
)	O
,	O
overall	O
completion	O
time	O
to	O
the	O
final	O
user	O
interface	O
is	O
faster	O
because	O
data	O
access	O
on	O
the	O
server-side	O
is	O
much	O
faster	O
than	O
client-side	O
API	O
requests	O
.	O
</s>
<s>
More	O
predictable	O
SEO	O
and	O
Site	O
Indexing	O
:	O
In	O
order	O
to	O
index	O
content	O
that	O
JavaScript	B-Language
apps	O
render	O
on	O
client-side	O
,	O
Googlebot	O
must	O
run	O
those	O
JavaScript	B-Language
apps	O
inside	O
a	O
full	O
browser	O
environment	O
and	O
capture	O
the	O
rendered	O
DOM	O
.	O
</s>
<s>
Also	O
,	O
because	O
JavaScript	B-Language
apps	O
can	O
make	O
AJAX	O
requests	O
for	O
further	O
rendering	O
,	O
Googlebot	O
must	O
have	O
a	O
policy	O
that	O
controls	O
apps’	O
network	O
access	O
.	O
</s>
<s>
These	O
are	O
why	O
getting	O
your	O
JavaScript	B-Language
app	O
indexed	O
properly	O
by	O
Googlebot	O
is	O
still	O
challenging	O
.	O
</s>
<s>
There	O
have	O
been	O
several	O
isomorphic	B-Language
JavaScript	I-Language
frameworks	O
and	O
libraries	O
created	O
,	O
most	O
notably	O
Meteor	B-Language
(	O
framework	O
)	O
.	O
</s>
