<s>
Web	B-Language
Components	I-Language
are	O
a	O
set	O
of	O
features	O
that	O
provide	O
a	O
standard	O
component	O
model	O
for	O
the	O
Web	O
allowing	O
for	O
encapsulation	B-Application
and	O
interoperability	O
of	O
individual	O
HTML	B-General_Concept
elements	I-General_Concept
.	O
</s>
<s>
Autonomous	O
custom	O
elements	O
are	O
HTML	B-General_Concept
elements	I-General_Concept
that	O
are	O
entirely	O
separated	O
from	O
native	O
HTML	B-General_Concept
elements	I-General_Concept
;	O
they	O
are	O
essentially	O
built	O
from	O
the	O
bottom	O
up	O
using	O
the	O
Custom	O
Elements	O
API	B-Application
.	O
</s>
<s>
Customized	O
built-in	O
elements	O
are	O
elements	O
that	O
are	O
built	O
upon	O
native	O
HTML	B-General_Concept
elements	I-General_Concept
to	O
reuse	O
their	O
functionality	O
.	O
</s>
<s>
Shadow	O
DOM	B-General_Concept
is	O
a	O
functionality	O
that	O
allows	O
the	O
web	B-Application
browser	I-Application
to	O
render	O
DOM	B-General_Concept
elements	O
without	O
putting	O
them	O
into	O
the	O
main	O
document	O
DOM	B-General_Concept
tree	I-General_Concept
.	O
</s>
<s>
This	O
creates	O
a	O
barrier	O
between	O
what	O
the	O
developer	O
and	O
the	O
browser	B-Application
can	O
reach	O
;	O
the	O
developer	O
cannot	O
access	O
the	O
Shadow	O
DOM	B-General_Concept
in	O
the	O
same	O
way	O
they	O
would	O
with	O
nested	O
elements	O
,	O
while	O
the	O
browser	B-Application
can	O
render	O
and	O
modify	O
that	O
code	O
the	O
same	O
way	O
it	O
would	O
with	O
nested	O
elements	O
.	O
</s>
<s>
The	O
impact	O
of	O
CSS	B-Language
scoped	O
within	O
the	O
Shadow	O
DOM	B-General_Concept
of	O
a	O
particular	O
element	O
is	O
that	O
HTML	B-General_Concept
elements	I-General_Concept
can	O
be	O
encapsulated	O
without	O
the	O
risk	O
of	O
CSS	B-Language
styles	I-Language
leaking	O
and	O
affecting	O
elements	O
that	O
they	O
were	O
not	O
supposed	O
to	O
affect	O
.	O
</s>
<s>
Although	O
these	O
elements	O
are	O
encapsulated	O
with	O
regard	O
to	O
HTML	B-Language
and	O
CSS	B-Language
,	O
they	O
can	O
still	O
fire	O
events	O
that	O
can	O
be	O
picked	O
up	O
by	O
other	O
elements	O
in	O
the	O
document	O
.	O
</s>
<s>
Shadow	O
DOM	B-General_Concept
must	O
always	O
be	O
connected	O
to	O
an	O
existing	O
element	O
,	O
either	O
through	O
attaching	O
it	O
as	O
a	O
literal	O
element	O
or	O
through	O
scripting	O
.	O
</s>
<s>
In	O
JavaScript	B-Language
,	O
Shadow	O
DOMs	B-General_Concept
are	O
attached	O
to	O
an	O
element	O
using	O
Element.attachShadow( )	O
.	O
</s>
<s>
HTML	B-Language
template	O
is	O
a	O
way	O
to	O
insert	O
chunks	O
of	O
HTML	B-Language
that	O
are	O
stamped	O
at	O
will	O
.	O
</s>
<s>
The	O
syntax	O
of	O
HTML	B-Language
templates	O
looks	O
like	O
this	O
:	O
</s>
<s>
Web	B-Language
Components	I-Language
are	O
supported	O
by	O
current	O
versions	O
of	O
all	O
major	O
browsers	B-Application
.	O
</s>
<s>
Backward	O
compatibility	O
with	O
older	O
browsers	B-Application
is	O
implemented	O
using	O
JavaScript-based	O
polyfills	B-Protocol
.	O
</s>
<s>
There	O
are	O
many	O
libraries	O
that	O
are	O
built	O
on	O
Web	B-Language
Components	I-Language
with	O
the	O
aim	O
of	O
increasing	O
the	O
level	O
of	O
abstraction	O
when	O
creating	O
custom	O
elements	O
.	O
</s>
<s>
From	O
the	O
above	O
list	O
,	O
Bosonic	O
,	O
Polymer	B-Language
,	O
Telepathy	O
and	O
DataFormsJS	O
,	O
all	O
provide	O
ready-made	O
components	O
that	O
are	O
free	O
to	O
use	O
.	O
</s>
<s>
While	O
Bosonic	O
,	O
Polymer	B-Language
&	O
DataFormsJS	O
have	O
far	O
more	O
pre-built	O
components	O
.	O
</s>
<s>
Telepathy	O
is	O
"	O
closest	O
to	O
the	O
metal	O
"	O
in	O
that	O
its	O
sole	O
focus	O
is	O
on	O
helping	O
the	O
developer	O
to	O
build	O
easily	O
maintained	O
webcomponents	B-Language
rapidly	O
.	O
</s>
<s>
There	O
are	O
numerous	O
community	O
efforts	O
for	O
the	O
Web	B-Language
Components	I-Language
ecosystem	O
.	O
</s>
<s>
WebComponents.org	O
provides	O
an	O
interface	O
to	O
search	O
for	O
any	O
existing	O
Web	B-Language
Components	I-Language
,	O
Custom	O
Elements	O
Everywhere	O
validates	O
whether	O
popular	O
front-end	O
frameworks	O
are	O
compatible	O
and	O
ready	O
to	O
use	O
Web	B-Language
Components	I-Language
standard	O
,	O
with	O
a	O
set	O
of	O
pending	O
bugs	O
and	O
available	O
workarounds	O
.	O
</s>
<s>
In	O
2011	O
,	O
Web	B-Language
Components	I-Language
were	O
introduced	O
for	O
the	O
first	O
time	O
by	O
Alex	O
Russell	O
at	O
Fronteers	O
Conference	O
.	O
</s>
<s>
In	O
2013	O
,	O
Polymer	B-Language
,	O
a	O
library	O
based	O
on	O
Web	B-Language
Components	I-Language
was	O
released	O
by	O
Google	B-Application
.	I-Application
</s>
<s>
In	O
2018	O
,	O
Angular	O
6	O
introduced	O
Angular	O
Elements	O
that	O
lets	O
you	O
package	O
your	O
Angular	O
components	O
as	O
custom	O
web	O
elements	O
,	O
which	O
are	O
part	O
of	O
the	O
web	B-Language
components	I-Language
set	O
of	O
web	O
platform	O
APIs	B-Application
.	O
</s>
<s>
In	O
2018	O
,	O
Firefox	B-Application
63	O
enabled	O
Web	B-Language
Components	I-Language
support	O
by	O
default	O
and	O
updated	O
the	O
developer	O
tools	O
to	O
support	O
them	O
.	O
</s>
