<s>
TypeScript	B-Language
is	O
a	O
free	B-License
and	I-License
open	I-License
source	I-License
high-level	B-Language
programming	I-Language
language	I-Language
developed	O
and	O
maintained	O
by	O
Microsoft	O
.	O
</s>
<s>
It	O
is	O
a	O
strict	O
syntactical	O
superset	O
of	O
JavaScript	B-Language
and	O
adds	O
optional	O
static	O
typing	O
to	O
the	O
language	O
.	O
</s>
<s>
It	O
is	O
designed	O
for	O
the	O
development	O
of	O
large	O
applications	O
and	O
transpiles	B-Language
to	O
JavaScript	B-Language
.	O
</s>
<s>
As	O
it	O
is	O
a	O
superset	O
of	O
JavaScript	B-Language
,	O
existing	O
JavaScript	B-Language
programs	O
are	O
also	O
valid	O
TypeScript	B-Language
programs	O
.	O
</s>
<s>
TypeScript	B-Language
may	O
be	O
used	O
to	O
develop	O
JavaScript	B-Language
applications	O
for	O
both	O
client-side	B-Operating_System
and	O
server-side	B-Application
execution	O
(	O
as	O
with	O
Node.js	B-Language
or	O
Deno	B-Application
)	O
.	O
</s>
<s>
Multiple	O
options	O
are	O
available	O
for	O
transpilation	B-Language
.	O
</s>
<s>
The	O
default	O
TypeScript	B-Language
Compiler	O
can	O
be	O
used	O
,	O
or	O
the	O
Babel	B-Language
compiler	O
can	O
be	O
invoked	O
to	O
convert	O
TypeScript	B-Language
to	O
JavaScript	B-Language
.	O
</s>
<s>
TypeScript	B-Language
supports	O
definition	O
files	O
that	O
can	O
contain	O
type	O
information	O
of	O
existing	O
JavaScript	B-Language
libraries	B-Library
,	O
much	O
like	O
C++	B-Language
header	B-Language
files	I-Language
can	O
describe	O
the	O
structure	O
of	O
existing	O
object	B-Application
files	I-Application
.	O
</s>
<s>
This	O
enables	O
other	O
programs	O
to	O
use	O
the	O
values	O
defined	O
in	O
the	O
files	O
as	O
if	O
they	O
were	O
statically	O
typed	O
TypeScript	B-Language
entities	O
.	O
</s>
<s>
There	O
are	O
third-party	O
header	B-Language
files	I-Language
for	O
popular	O
libraries	B-Library
such	O
as	O
jQuery	B-Language
,	O
MongoDB	B-Application
,	O
and	O
D3.js	B-Language
.	O
</s>
<s>
TypeScript	B-Language
headers	O
for	O
the	O
Node.js	B-Language
library	O
modules	B-Architecture
are	O
also	O
available	O
,	O
allowing	O
development	O
of	O
Node.js	B-Language
programs	O
within	O
TypeScript	B-Language
.	O
</s>
<s>
The	O
TypeScript	B-Language
compiler	O
is	O
itself	O
written	O
in	O
TypeScript	B-Language
and	O
compiled	B-Language
to	O
JavaScript	B-Language
.	O
</s>
<s>
It	O
is	O
licensed	O
under	O
the	O
Apache	B-Application
License	I-Application
2.0	I-Application
.	O
</s>
<s>
Anders	O
Hejlsberg	O
,	O
lead	O
architect	O
of	O
C#	B-Application
and	O
creator	O
of	O
Delphi	B-Language
and	O
Turbo	B-Application
Pascal	I-Application
,	O
has	O
worked	O
on	O
the	O
development	O
of	O
TypeScript	B-Language
.	O
</s>
<s>
TypeScript	B-Language
was	O
released	O
to	O
the	O
public	O
in	O
October	O
2012	O
,	O
with	O
version	O
0.8	O
,	O
after	O
two	O
years	O
of	O
internal	O
development	O
at	O
Microsoft	O
.	O
</s>
<s>
Soon	O
after	O
the	O
initial	O
public	O
release	O
,	O
Miguel	O
de	O
Icaza	O
praised	O
the	O
language	O
itself	O
,	O
but	O
criticized	O
the	O
lack	O
of	O
mature	O
IDE	O
support	O
apart	O
from	O
Microsoft	B-Application
Visual	I-Application
Studio	I-Application
,	O
which	O
was	O
not	O
available	O
on	O
Linux	B-Application
and	O
OS	B-Application
X	I-Application
at	O
that	O
time	O
.	O
</s>
<s>
As	O
of	O
April	O
2021	O
there	O
is	O
support	O
in	O
other	O
IDEs	O
and	O
text	O
editors	O
,	O
including	O
Emacs	B-Application
,	O
Vim	B-Application
,	O
WebStorm	O
,	O
Atom	B-Application
and	O
Microsoft	O
's	O
own	O
Visual	O
Studio	O
Code.TypeScript	O
0.9	O
,	O
released	O
in	O
2013	O
,	O
added	O
support	O
for	O
generics	B-Language
.	O
</s>
<s>
TypeScript	B-Language
1.0	O
was	O
released	O
at	O
Microsoft	O
's	O
Build	O
developer	O
conference	O
in	O
2014	O
.	O
</s>
<s>
Visual	B-Application
Studio	I-Application
2013	I-Application
Update	O
2	O
provides	O
built-in	O
support	O
for	O
TypeScript	B-Language
.	O
</s>
<s>
Further	O
improvement	O
were	O
made	O
in	O
July	O
2014	O
,	O
when	O
the	O
development	O
team	O
announced	O
a	O
new	O
TypeScript	B-Language
compiler	O
,	O
asserted	O
to	O
have	O
a	O
five-fold	O
performance	O
increase	O
.	O
</s>
<s>
Simultaneously	O
,	O
the	O
source	O
code	O
,	O
which	O
was	O
initially	O
hosted	O
on	O
CodePlex	B-Protocol
,	O
was	O
moved	O
to	O
GitHub	B-Application
.	O
</s>
<s>
On	O
22	O
September	O
2016	O
,	O
TypeScript	B-Language
2.0	O
was	O
released	O
,	O
introducing	O
several	O
features	O
,	O
including	O
the	O
ability	O
for	O
programmers	O
to	O
optionally	O
enforce	O
null	B-Application
safety	I-Application
,	O
sometimes	O
referred	O
to	O
as	O
the	O
billion-dollar	O
mistake	O
.	O
</s>
<s>
TypeScript	B-Language
3.0	O
was	O
released	O
on	O
30	O
July	O
2018	O
,	O
bringing	O
many	O
language	O
additions	O
like	O
tuples	B-Application
in	O
rest	O
parameters	O
and	O
spread	O
expressions	O
,	O
rest	O
parameters	O
with	O
tuple	B-Application
types	O
,	O
generic	B-Language
rest	O
parameters	O
and	O
so	O
on	O
.	O
</s>
<s>
TypeScript	B-Language
4.0	O
was	O
released	O
on	O
20	O
August	O
2020	O
.	O
</s>
<s>
While	O
4.0	O
did	O
not	O
introduce	O
any	O
breaking	O
changes	O
,	O
it	O
added	O
language	O
features	O
such	O
as	O
Custom	O
JSX	O
Factories	O
and	O
Variadic	O
Tuple	B-Application
Types	O
.	O
</s>
<s>
TypeScript	B-Language
5.0	O
was	O
released	O
on	O
16	O
March	O
2023	O
.	O
</s>
<s>
TypeScript	B-Language
originated	O
from	O
the	O
shortcomings	O
of	O
JavaScript	B-Language
for	O
the	O
development	O
of	O
large-scale	O
applications	O
both	O
at	O
Microsoft	O
and	O
among	O
their	O
external	O
customers	O
.	O
</s>
<s>
Challenges	O
with	O
dealing	O
with	O
complex	O
JavaScript	B-Language
code	O
led	O
to	O
demand	O
for	O
custom	O
tooling	O
to	O
ease	O
developing	O
of	O
components	O
in	O
the	O
language	O
.	O
</s>
<s>
TypeScript	B-Language
developers	O
sought	O
a	O
solution	O
that	O
would	O
not	O
break	O
compatibility	O
with	O
the	O
standard	O
and	O
its	O
cross-platform	O
support	O
.	O
</s>
<s>
Knowing	O
that	O
the	O
current	O
ECMAScript	B-Language
standard	O
proposal	O
promised	O
future	O
support	O
for	O
class-based	B-Application
programming	I-Application
,	O
TypeScript	B-Language
was	O
based	O
on	O
that	O
proposal	O
.	O
</s>
<s>
That	O
led	O
to	O
a	O
JavaScript	B-Language
compiler	O
with	O
a	O
set	O
of	O
syntactical	O
language	O
extensions	O
,	O
a	O
superset	O
based	O
on	O
the	O
proposal	O
,	O
that	O
transforms	O
the	O
extensions	O
into	O
regular	O
JavaScript	B-Language
.	O
</s>
<s>
In	O
this	O
sense	O
,	O
the	O
class	O
feature	O
of	O
TypeScript	B-Language
was	O
a	O
preview	O
of	O
what	O
to	O
expect	O
from	O
ECMAScript	B-Language
2015	O
.	O
</s>
<s>
A	O
unique	O
aspect	O
not	O
in	O
the	O
proposal	O
,	O
but	O
added	O
to	O
TypeScript	B-Language
,	O
is	O
optional	O
static	O
typing	O
(	O
also	O
known	O
as	O
gradual	O
typing	O
)	O
that	O
enables	O
static	O
language	O
analysis	O
to	O
facilitate	O
tooling	O
and	O
IDE	O
support	O
.	O
</s>
<s>
TypeScript	B-Language
adds	O
support	O
for	O
features	O
such	O
as	O
classes	O
,	O
modules	B-Architecture
,	O
and	O
an	O
arrow	B-General_Concept
function	I-General_Concept
syntax	O
as	O
defined	O
in	O
the	O
ECMAScript	B-Language
2015	O
standard	O
.	O
</s>
<s>
TypeScript	B-Language
is	O
a	O
language	O
extension	O
that	O
adds	O
features	O
to	O
ECMAScript	B-Language
6	O
.	O
</s>
<s>
The	O
following	O
features	O
are	O
backported	O
from	O
ECMAScript	B-Language
2015	O
:	O
</s>
<s>
Syntactically	O
,	O
TypeScript	B-Language
is	O
very	O
similar	O
to	O
JScript	B-Language
.NET	I-Language
,	O
another	O
Microsoft	O
implementation	O
of	O
the	O
ECMA-262	B-Language
language	O
standard	O
that	O
added	O
support	O
for	O
static	O
typing	O
and	O
classical	O
object-oriented	B-Language
language	I-Language
features	O
such	O
as	O
classes	O
,	O
inheritance	O
,	O
interfaces	B-Application
,	O
and	O
namespaces	O
.	O
</s>
<s>
TypeScript	B-Language
is	O
a	O
strict	O
superset	O
of	O
ECMAScript	B-Language
2015	O
,	O
which	O
is	O
itself	O
a	O
superset	O
of	O
ECMAScript	B-Language
5	O
,	O
commonly	O
referred	O
to	O
as	O
JavaScript	B-Language
.	O
</s>
<s>
As	O
such	O
,	O
a	O
JavaScript	B-Language
program	O
is	O
also	O
a	O
valid	O
TypeScript	B-Language
program	O
,	O
and	O
a	O
TypeScript	B-Language
program	O
can	O
seamlessly	O
consume	O
JavaScript	B-Language
.	O
</s>
<s>
By	O
default	O
the	O
compiler	O
targets	O
ECMAScript	B-Language
5	O
,	O
the	O
current	O
prevailing	O
standard	O
,	O
but	O
is	O
also	O
able	O
to	O
generate	O
constructs	O
used	O
in	O
ECMAScript	B-Language
3	O
or	O
2015	O
.	O
</s>
<s>
With	O
TypeScript	B-Language
,	O
it	O
is	O
possible	O
to	O
use	O
existing	O
JavaScript	B-Language
code	O
,	O
incorporate	O
popular	O
JavaScript	B-Language
libraries	B-Library
,	O
and	O
call	O
TypeScript-generated	O
code	O
from	O
other	O
JavaScript	B-Language
.	O
</s>
<s>
Type	O
declarations	O
for	O
these	O
libraries	B-Library
are	O
provided	O
with	O
the	O
source	O
code	O
.	O
</s>
<s>
TypeScript	B-Language
provides	O
static	O
typing	O
through	O
type	O
annotations	O
to	O
enable	O
type	O
checking	O
at	O
compile	B-Application
time	I-Application
.	O
</s>
<s>
This	O
is	O
optional	O
and	O
can	O
be	O
ignored	O
to	O
use	O
the	O
regular	O
dynamic	O
typing	O
of	O
JavaScript	B-Language
.	O
</s>
<s>
Typescript	B-Language
also	O
supports	O
data	O
types	O
with	O
following	O
annotations	O
Array	O
,	O
Enums	B-Language
,	O
void	O
.	O
</s>
<s>
Additional	O
data	O
types	O
are	O
:	O
Tuple	B-Application
,	O
Union	O
,	O
never	O
and	O
any	O
.	O
</s>
<s>
An	O
array	O
with	O
predefined	O
data	O
types	O
at	O
each	O
index	O
is	O
Tuple	B-Application
type	O
.	O
</s>
<s>
Type	O
annotations	O
can	O
be	O
exported	O
to	O
a	O
separate	O
declarations	O
file	O
to	O
make	O
type	O
information	O
available	O
for	O
TypeScript	B-Language
scripts	O
using	O
types	O
already	O
compiled	B-Language
into	O
JavaScript	B-Language
.	O
</s>
<s>
Annotations	O
can	O
be	O
declared	O
for	O
an	O
existing	O
JavaScript	B-Language
library	O
,	O
as	O
has	O
been	O
done	O
for	O
Node.js	B-Language
and	O
jQuery	B-Language
.	O
</s>
<s>
The	O
TypeScript	B-Language
compiler	O
makes	O
use	O
of	O
type	O
inference	O
to	O
infer	O
types	O
when	O
types	O
are	O
not	O
given	O
.	O
</s>
<s>
A	O
value	O
of	O
the	O
any	O
type	O
supports	O
the	O
same	O
operations	O
as	O
a	O
value	O
in	O
JavaScript	B-Language
and	O
minimal	O
static	O
type	O
checking	O
is	O
performed	O
for	O
operations	O
on	O
any	O
values	O
.	O
</s>
<s>
When	O
a	O
TypeScript	B-Language
script	O
gets	O
compiled	B-Language
there	O
is	O
an	O
option	O
to	O
generate	O
a	O
declaration	O
file	O
(	O
with	O
the	O
extension	O
.d.ts	O
)	O
that	O
functions	O
as	O
an	O
interface	B-Application
to	O
the	O
components	O
in	O
the	O
compiled	B-Language
JavaScript	B-Language
.	O
</s>
<s>
The	O
resulting	O
declaration	O
file	O
can	O
then	O
be	O
used	O
to	O
describe	O
the	O
exported	O
virtual	O
TypeScript	B-Language
types	O
of	O
a	O
JavaScript	B-Language
library	O
or	O
module	B-Architecture
when	O
a	O
third-party	O
developer	O
consumes	O
it	O
from	O
TypeScript	B-Language
.	O
</s>
<s>
The	O
concept	O
of	O
declaration	O
files	O
is	O
analogous	O
to	O
the	O
concept	O
of	O
header	B-Language
file	I-Language
found	O
in	O
C/C	B-Language
++	I-Language
.	O
</s>
<s>
Type	O
declaration	O
files	O
can	O
be	O
written	O
by	O
hand	O
for	O
existing	O
JavaScript	B-Language
libraries	B-Library
,	O
as	O
has	O
been	O
done	O
for	O
jQuery	B-Language
and	O
Node.js	B-Language
.	O
</s>
<s>
Large	O
collections	O
of	O
declaration	O
files	O
for	O
popular	O
JavaScript	B-Language
libraries	B-Library
are	O
hosted	O
on	O
GitHub	B-Application
in	O
.	O
</s>
<s>
TypeScript	B-Language
supports	O
ECMAScript	B-Language
2015	O
classes	O
that	O
integrate	O
the	O
optional	O
type	O
annotations	O
support	O
.	O
</s>
<s>
TypeScript	B-Language
supports	O
generic	B-Language
programming	I-Language
.	O
</s>
<s>
TypeScript	B-Language
distinguishes	O
between	O
modules	B-Architecture
and	O
namespaces	O
.	O
</s>
<s>
Both	O
features	O
in	O
TypeScript	B-Language
support	O
encapsulation	O
of	O
classes	O
,	O
interfaces	B-Application
,	O
functions	O
and	O
variables	O
into	O
containers	O
.	O
</s>
<s>
Namespaces	O
(	O
formerly	O
internal	O
modules	B-Architecture
)	O
utilize	O
immediately-invoked	B-Language
function	I-Language
expression	I-Language
of	O
JavaScript	B-Language
to	O
encapsulate	O
code	O
,	O
whereas	O
modules	B-Architecture
(	O
formerly	O
external	O
modules	B-Architecture
)	O
leverage	O
JavaScript	B-Language
library	O
patterns	O
to	O
do	O
so	O
(	O
AMD	B-Language
or	O
CommonJS	B-Language
)	O
.	O
</s>
<s>
The	O
TypeScript	B-Language
compiler	O
,	O
named	O
tsc	O
,	O
is	O
written	O
in	O
TypeScript	B-Language
.	O
</s>
<s>
As	O
a	O
result	O
,	O
it	O
can	O
be	O
compiled	B-Language
into	O
regular	O
JavaScript	B-Language
and	O
can	O
then	O
be	O
executed	O
in	O
any	O
JavaScript	B-Language
engine	O
(	O
e.g.	O
</s>
<s>
It	O
is	O
also	O
available	O
as	O
a	O
Node.js	B-Language
package	O
that	O
uses	O
Node.js	B-Language
as	O
a	O
host	O
.	O
</s>
<s>
The	O
current	O
version	O
of	O
the	O
compiler	O
supports	O
ECMAScript	B-Language
5	O
by	O
default	O
.	O
</s>
<s>
An	O
option	O
is	O
allowed	O
to	O
target	O
ECMAScript	B-Language
2015	O
to	O
make	O
use	O
of	O
language	O
features	O
exclusive	O
to	O
that	O
version	O
(	O
e.g.	O
</s>
<s>
Classes	O
,	O
despite	O
being	O
part	O
of	O
the	O
ECMAScript	B-Language
2015	O
standard	O
,	O
are	O
available	O
in	O
both	O
modes	O
.	O
</s>
<s>
Microsoft	O
provides	O
a	O
plug-in	B-Application
for	O
Visual	B-Application
Studio	I-Application
2012	I-Application
and	O
WebMatrix	B-Application
,	O
full	O
integrated	O
support	O
in	O
Visual	B-Application
Studio	I-Application
2013	I-Application
,	O
Visual	B-Application
Studio	I-Application
2015	I-Application
,	O
and	O
basic	O
text	O
editor	O
support	O
for	O
Emacs	B-Application
and	O
Vim	B-Application
.	O
</s>
<s>
Visual	B-Language
Studio	I-Language
Code	I-Language
is	O
a	O
(	O
mostly	O
)	O
open-source	O
,	O
cross-platform	O
source	O
code	O
editor	O
developed	O
by	O
Microsoft	O
based	O
on	O
Electron	B-Operating_System
.	O
</s>
<s>
It	O
supports	O
TypeScript	B-Language
in	O
addition	O
to	O
several	O
other	O
languages	O
,	O
and	O
offers	O
features	O
like	O
debugging	O
and	O
intelligent	B-Application
code	I-Application
completion	I-Application
.	O
</s>
<s>
alm.tools	O
is	O
an	O
open	O
source	O
cloud	O
IDE	O
for	O
TypeScript	B-Language
built	O
using	O
TypeScript	B-Language
,	O
ReactJS	O
and	O
TypeStyle	O
.	O
</s>
<s>
JetBrains	O
supports	O
TypeScript	B-Language
with	O
code	O
completion	O
,	O
refactoring	O
and	O
debugging	O
in	O
its	O
IDEs	O
built	O
on	O
IntelliJ	B-Language
platform	O
,	O
such	O
as	O
PhpStorm	O
6	O
,	O
WebStorm	O
6	O
,	O
and	O
IntelliJ	B-Language
IDEA	I-Language
,	O
as	O
well	O
as	O
their	O
Visual	B-Application
Studio	I-Application
Add-in	B-Application
and	O
extension	O
,	O
ReSharper	O
8.1	O
.	O
</s>
<s>
Atom	B-Application
has	O
a	O
TypeScript	B-Language
plugin	B-Application
with	O
support	O
for	O
code	O
completion	O
,	O
navigation	O
,	O
formatting	O
,	O
and	O
fast	O
compilation	O
.	O
</s>
<s>
The	O
online	O
Cloud9	B-Application
IDE	I-Application
and	O
Codenvy	B-Language
support	O
TypeScript	B-Language
.	O
</s>
<s>
A	O
plugin	B-Application
is	O
available	O
for	O
the	O
NetBeans	B-Application
IDE	I-Application
.	O
</s>
<s>
TypEcs	O
is	O
available	O
for	O
the	O
Eclipse	B-Application
IDE	I-Application
.	O
</s>
<s>
The	O
Cross	O
Platform	O
Cloud	O
IDE	O
Codeanywhere	O
supports	O
TypeScript	B-Language
.	O
</s>
<s>
Webclipse	O
An	O
Eclipse	B-Application
plugin	B-Application
designed	O
to	O
develop	O
TypeScript	B-Language
and	O
Angular	B-Language
2	I-Language
.	O
</s>
<s>
Angular	B-Language
IDE	O
A	O
standalone	O
IDE	O
available	O
via	O
npm	O
to	O
develop	O
TypeScript	B-Language
and	O
Angular	B-Language
2	I-Language
applications	O
,	O
with	O
integrated	O
terminal	O
support	O
.	O
</s>
<s>
Tide	O
TypeScript	B-Language
Interactive	O
Development	O
Environment	O
for	O
Emacs	B-Application
.	O
</s>
<s>
Using	O
plug-ins	B-Application
,	O
TypeScript	B-Language
can	O
be	O
integrated	O
with	O
build	B-Application
automation	I-Application
tools	O
,	O
including	O
Grunt	O
(	O
grunt-ts	O
)	O
,	O
Apache	B-Language
Maven	I-Language
(	O
TypeScript	B-Language
Maven	B-Language
Plugin	B-Application
)	O
,	O
Gulp	O
(	O
gulp-typescript	O
)	O
and	O
Gradle	B-Language
(	O
TypeScript	B-Language
Gradle	B-Language
Plugin	B-Application
)	O
.	O
</s>
<s>
TSLint	O
scans	O
TypeScript	B-Language
code	O
for	O
conformance	O
to	O
a	O
set	O
of	O
standards	O
and	O
guidelines	O
.	O
</s>
<s>
ESLint	B-Language
,	O
a	O
standard	O
JavaScript	B-Language
linter	O
,	O
also	O
provided	O
some	O
support	O
for	O
TypeScript	B-Language
via	O
community	O
plugins	B-Application
.	O
</s>
<s>
However	O
,	O
ESLint	B-Language
's	O
inability	O
to	O
leverage	O
TypeScript	B-Language
's	O
language	O
services	O
precluded	O
certain	O
forms	O
of	O
semantic	O
linting	O
and	O
program-wide	O
analysis	O
.	O
</s>
<s>
In	O
early	O
2019	O
,	O
the	O
TSLint	O
team	O
announced	O
the	O
linter	O
's	O
deprecation	O
in	O
favor	O
of	O
typescript-eslint	O
,	O
a	O
joint	O
effort	O
of	O
the	O
TSLint	O
,	O
ESLint	B-Language
and	O
TypeScript	B-Language
teams	O
to	O
consolidate	O
linting	O
under	O
the	O
ESLint	B-Language
umbrella	O
for	O
improved	O
performance	O
,	O
community	O
unity	O
and	O
developer	O
accessibility	O
.	O
</s>
