I am just getting into the JS ecosystem and I have 4 years of experience in the python ecosystem.
I wanted to know if there is a direct equivalent of pydantic or dataclasses equivalent in JS (not typescript).
I am aware that json schema would be a worthy replacement but wanted class based capabilities if possible.
Top comments (1)
In JavaScript, there is no direct equivalent to the pydantic or dataclasses libraries in Python. However, there are a few libraries that offer similar functionality and can be used as alternatives.
One option is the
class-validator
library, which allows you to define class-based data models and apply validation constraints to their properties. This library is similar to pydantic in that it allows you to define data models and apply validation rules to them, but it is implemented as a set of decorators that you can use to annotate your classes.Here is an example of how you might use the
class-validator
library to define and validate a data model in JavaScript:import { IsString, MinLength } from 'class-validator'; class User { @IsString() @MinLength(3) username: string; } const user = new User(); user.username = 'abc'; console.log(validateSync(user)); // Output: { username: [] } (no errors) user.username = 'ab'; console.log(validateSync(user)); // Output: { username: [{...}] } (errors)
In this example, the
User
class is defined using theclass-validator
library. Theusername
property is annotated with theIsString
andMinLength
decorators, which specify that the property must be a string and have a minimum length of 3 characters.The
validateSync
function is then used to validate theuser
instance, and the resulting errors (if any) are logged to the console.Another option is the
class-transformer
library, which allows you to define class-based data models and automatically convert them to and from plain JavaScript objects (similar to thedataclasses.asdict
anddataclasses.fromdict
functions in Python). This library is useful for working with data in APIs or other contexts where you need to convert between class-based and plain JavaScript objects.Here is an example of how you might use the
class-transformer
library to define and convert a data model in JavaScript:import { Expose } from 'class-transformer'; class User { @Expose() username: string; } const user = new User(); user.username = 'abc'; console.log(plainToClass(User, { username: 'abc' })); // Output: User { username: 'abc' } console.log(classToPlain(user)); // Output: { username: 'abc' }
In this example, the
User
class is defined using theclass-transformer
library. Theusername
property is annotated with theExpose
decorator, which specifies that the property should be included when converting the class to and from a plain JavaScript object.The
plainToClass
andclassToPlain
functions are then used to convert between theUser
class and a plain JavaScript object, and the results are logged to the console.Overall, while there is no direct equivalent to pydantic or dataclasses in JavaScript, the
class-validator
andclass-transformer
libraries offer similar functionality and can be used as alternatives.I'm an experimental help bot that leverages ChatGPT. As such, the answers I provide may be incorrect, incomplete, or even nonsensical. I am not associated with OpenAI.
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