incoming-ts

Incoming is a TypeScript package that aims to support data validation both on the server and the client side. It is based on decorators and uses them to validate incoming objects of your choice.

Table of contents

• Instalation
• Usage
  • Server
  • Client
• Available decorators

Installation

$npm install incoming-ts

Usage

Note: Decorators are an experimental feature in TypeScript and are in stage 2 proposal for JavaScript. To enable experimental support for decorators in TypeScript, you must enable the experimentalDecorators compiler option either on the command line or in your tsconfig.json.

Command Line:

$tsc --target ES5 --experimentalDecorators

tsconfig.json:

{
  "compilerOptions": {
    "target": "ES5",
    "experimentalDecorators": true
  }
}

Examples

Server

Example usage for object validation received via post request before saving it as new document in Mongoose model in MongoDB databse handled in Express:

Step 1

First create a class with properties that match properties of the object that you want to validate. To add validation conditions, simply annotate selected properties with chosen decorators. You can chain validation coditions by adding multiple decorators. The validation will be performed from bottom decorator to the top for each property. You can find a full list of currently available decorators in the section Available decorators.

import {MaxLength, IsAlphaNumeric, IsLength, IsEmail} from 'incoming-ts';

class Incoming {
  @MaxLength(30)
  @IsAlphaNumeric()
  title: string;

  @IsLength(10, 30)
  IsAlphaNumeric();
  description: string;

  @IsEmail()
  author: string;

  constructor(title: string, description: string, author: string) {
    this.title = title;
    this.description = description;
    this.author = author;
  }
}

Step 2

Inside the function that serves the request, destructure the chosen properties from req.body. Then create a new instance of your Incoming class. The validation will take place in the moment that instantiation happens. If it fails the error will be thrown and the property that did not pass validation will not be created. The example assumes that the Mongoose Model Schema requires all properties before creating the document, hence it will not be created.

If the validation passes the new document will be created.

async function servePostRequest(req: Request, res: Response): Promise<any> {
  try {
    const {title, description, author} = req.body;
    const incoming = new Incoming(title, description, author);
    const result = await Model.create(incoming);
    //send response
  } catch (error) {
    //handle error
  }
}

Client

Example usage in an Angular application to serve submitting a form and sending a post request:

Step 1

First create a class with properties that match properties of the object that you want to validate. To add validation conditions, simply annotate selected properties with chosen decorators. You can chain validation coditions by adding multiple decorators. The validation will be performed from bottom decorator to the top for each property. You can find a full list of currently available decorators in the section Available decorators.

import {MinLength, IsAlphaNumeric} from 'incoming-ts';

class Incoming {
  @MinLength(3)
  @IsAlphaNumeric()
  allergy: string;

  constructor(allergy: string) {
    this.allergy = allergy;
  }
}

Step 2

Then inside the function that handles the form submission create an instance of Incoming class with expected properties. The validation will take place in the moment that instantiation happens. If it fails the error will be thrown and the property that did not pass validation will not be created.

onSubmit (): void {

  const newAllergy: Allergy = this.allergyForm.value;
  const incoming = new Incoming(newAllergy.allergy);

	this.allergyService.postAllergy(incoming)
    .subscribe((allergy) => {
      this.allergyService.addToAllergies([allergy])
    });
}

Available decorators

Here you can find all currently available decorators and their behaviour. Each validator will throw an error in case the validation fails (i.e. the condition has not been met). In addition, some decorators perform extra type checks.

Decorator	Behaviour
@Contains(word: string)	Condition: the property value contains word. If it will encounter value of type different than string it will throw an error.
@Equals(value: string)	Condition: the property value equals to provided value. If it will encounter value of type different than string it will throw an error.
@IsAlphaNumeric()	Condition: the property value is alphanumeric.
@IsArray()	Condition: the property value is an array.
@IsBoolean()	Condition: the property value is a boolean.
@IsDateObj()	Condition: the property value is a Date object.
@IsDecimalNum()	Condition: the property value is a decimal number. If it will encounter value of type different than number it will throw an error.
@IsEmail()	Condition: the property value is a string in format [e-mail]. If it will encounter value of type different than string it will throw an error.
@IsLength(min: number, max: number)	Condition: the property value has length in range (min-max) inclusive. If it will encounter value of type different than string or object that is not an array it will throw an error.
@IsLowerCase()	Condition: the property value is lowercase string. If it will encounter value of type different than string it will throw an error.
@IsNumber()	Condition: the property value is of type number.
@IsUpperCase()	Condition: the property value is uppercase string. If it will encounter value of type different than string it will throw an error.
@MaxLength(max: number)	Condition: the property value has length no grater than max. If it will encounter value of type different than string or object that is not an array it will throw an error.
@MaxNum(max: number)	Condition: the property value is not grater than max. If it will encounter value of type different than number it will throw an error.
@MinLength(min: number)	Condition: the property value has length not less than min. If it will encounter value of type different than string or object that is not an array it will throw an error.
@MinNum(min: number)	Condition: the property value is not less than min. If it will encounter value of type different than number it will throw an error.
@NotEmpty()	Condition: the property value is not null, an empty string, array or key-value pair object.
@OnlyLetters()	Condition: the property value contains only letters. If it will encounter value of type different than string it will throw an error.