NestJs
along with
class-validator
is a good combination for validating API responses. Both are well documented but some needed use cases are not covered assuming developer to figure out. Below are some few cheat sheets which helped me in defining those cases and you can use these to scale to some extent.
}
from
'
class-validator
'
const
weekdays
=
[
'
monday
'
,
'
tuesday
'
,
'
wednesday
'
,
'
thursday
'
,
'
friday
'
];
export
class
SpecificString
{
@
IsArray
()
@
ArrayNotEmpty
()
@
IsIn
(
weekdays
)
day
:
string
[]
// check if every array item is string
@
IsString
({
each
:
true
})
// Pass `each: true` when you want this validation to run on every array item
// Check if every array item has max length
@
MaxLength
(
6
,
{
each
:
true
})
// Check if every array item is only alphabets
@
Matches
(
'
^[a-zA-Z
\\
s]+$
'
,
undefined
,
{
each
:
true
})
// CHeck if every array item contains a text
@
Contains
(
'
hello
'
,
{
each
:
true
})
stringArray
:
string
[]
}
from
'
class-validator
'
@
ValidatorConstraint
({
name
:
'
arrayPrefixValidator
'
})
export
class
ArrayPrefixValidator
implements
ValidatorConstraintInterface
{
validate
(
values
:
string
[]
=
[]):
boolean
{
if
(
values
.
length
)
{
return
values
.
every
((
value
)
=>
value
.
startsWith
(
'
str-
'
))
return
false
export
class
StringArray
{
@
IsArray
()
@
ArrayNotEmpty
()
// Check if every array item contains a prefix str-
@
Validate
(
ArrayPrefixValidator
,
{
message
:
'
No str- prefix
'
})
stringArray
:
string
[]
@
ValidatorConstraint
({
name
:
'
isDividedBy17
'
})
export
class
IsDividedBy17
implements
ValidatorConstraintInterface
{
validate
(
value
:
number
):
boolean
{
if
(
value
{
return
value
%
17
===
0
return
false
export
class
SpecificNumber
{
@
IsNumber
()
@
IsNotEmpty
()
// Check if number is divisible by 17
@
Validate
(
IsDividedBy17
,
{
message
:
'
No divided by 17
'
})
specificNumber
:
number
@
ValidatorConstraint
({
name
:
'
isEvenNumber
'
})
export
class
IsEvenNumber
implements
ValidatorConstraintInterface
{
validate
(
numbers
:
number
):
boolean
{
if
(
numbers
{
return
numbers
.
every
(
number
=>
number
%
2
===
0
)
return
false
export
class
SpecificNumber
{
@
IsNumber
()
@
IsNotEmpty
()
// Check if everynumber is even
@
Validate
(
IsEvenNumber
,
{
message
:
'
No divided by 17
'
})
numbersList
:
number
[]
yearOfRelease:
2012
,
languages:
[
"en"
,
"fr"
,
"es"
]
gener:
[
"animation"
,
"kids"
]
@
ValidatorConstraint
({
name
:
'
isEvenNumber
'
})
export
class
IsEvenNumber
implements
ValidatorConstraintInterface
{
validate
(
numbers
:
number
):
boolean
{
if
(
numbers
{
return
numbers
.
every
(
number
=>
number
%
2
===
0
)
return
false
const
validLanguages
=
[
"
en
"
,
"
es
"
,
"
fr
"
]
const
validGeneres
=
[
"
sci-fi
"
,
"
thriller
"
,
"
animation
"
,
"
horror
"
,
"
vintage
"
]
// 💡 Types here
export
class
Movie
{
@
IsString
()
@
IsNotEmpty
()
@
ISRequired
()
name
:
string
@
IsNotEmpty
()
@
IsNumber
()
@
ISRequired
()
yearOfRelease
:
number
@
IsNotEmpty
()
@
IsString
()
@
IsIn
(
validLanguages
)
@
ISRequired
()
languages
:
string
[]
@
IsNotEmpty
()
@
IsString
()
@
IsIn
(
validGeneres
)
@
ISRequired
()
genre
:
string
[]
export
class
MoviesList
{
@
IsArray
()
@
ArrayNotEmpty
()
@
Type
(()
=>
Movie
)
movies
:
Movie
[]
