@buka/class-transformer-extra

@buka/class-transformer-extra contains methods that's aren't included in the class-transformer package.

Install

npm install @buka/class-transformer-extra class-transformer
# OR
yarn install @buka/class-transformer-extra class-transformer
# OR
pnpm install @buka/class-transformer-extra class-transformer

Usage

String

method	before transformer	after transformer
@Split(",")	"a,b,c"	["a", "b", "c"]
@Trim()	" abc "	"abc"
@ToString({ optional: true })	123	"123"
@ToLowerCase()	"ABC"	"abc"
@ToUpperCase()	"abc"	"ABC"
@Replace("-", "_")	"a-b-c"	"a_b_c"

@Split, @Trim, @ToLowerCase, @ToUpperCase and @Replace will do nothing if the value isn't string. When set optional: true, undefined will not be transformed.

Date

method	before transformer	after transformer
@ToDate({ optional: true })	"2024-01-01"	new Date("2024-01-01")
@FormatDate("YYYY/MM/DD", { optional: true })	"2024-01-01"	"2024/01/01"

Number

method	before transformer	after transformer
@ToNumber({ optional: true })	"123"	123
@ToBigInt({ optional: true })	"123"	123n

ToNumber() and @ToBigInt() will return NaN if the value isn't number

Boolean

method	before transformer	after transformer
@ToBoolean()	1	true

ToBoolean() has multiple parameters to adapt to different needs, examples:

ToBoolean(v => Boolean(v)), { optional: true }): If the value is undefined, do nothing. Otherwise, v => Boolean(v) will be used to transform value.

ToBoolean(['0', 'false', false], { optional: true }):

If the value is '0' or 'false' or false, transform to false, and if the value is undefined, do nothing, otherwise value will be transform to true.

Array

method	before transformer	after transformer
@Filter((num: number) => num > 3)	[1,2,3.4,5]	[4,5]
@Flatten()	[1, [2, [3, 4, [5]]]]	[1,2,3,4,5]
@Uniq()	[1,1,2,3,4,4,5]	[1,2,3,4,5]
@UniqBy(Math.abs)	[-1, 1, 2, 3, -3]	[-1, 2, 3]

@Filter, @Flatten, @Uniq and @UniqBy will do nothing if the value isn't array.

Contribute

If you want to report bug or add new decorators, please submit an Issue or Pull Request.

Q&A

1. Why can't it be used with the @IsOptional decorator?

   The latest version of class-validator@^0.14.1 is not set metadata that can identify @IsOptional. If the identifiers are added in later versions, I will also follow up. And the identifier had be add in develop branch of class-validator.