creating-your-middleware.md

Creating your middleware

JZOR is extensible. You can create and register your own middleware.

Let's create a custom middleware now!

Recreating the allow middleware

In this sample, we will recreate the allow middleware, that indicates if the value is inside the range of the allow, it will be considered as a valid value.

const schema = {
  $type: 'string',
  allow: [null] // <- will accept the "null" as a valid value.
}

const value = null

const allowMiddleware = {
  // first we need to indicate the name of the attribute that will be
  // used in the schema.
  $attr: 'allow',

  // the attribute "pre" set to true indicates this middleware will run
  // BEFORE other validations.
  pre: true,

  // if you pass the attribute "post" set to true, it will rul AFTER
  // other validations.
  post: true,

  // the "validate" function is the function that will handle the
  // validation and must return an object with a property "handled".
  // The property "handled" indicates if it needs to continue the
  // validation or not.
  
  validate: ctx => {
    // the ctx.value prop contain the value to be validated.
    // in this sample, the ctx.value is: "null"
    const value = ctx.value

    // the ctx.schema contains the schema for your value.
    // in this sample, the ctx.schema is:
    // {
    //   $type: 'string',
    //   allow: [null]
    // }
    const schema = ctx.schema

    // with this data, you can create all rules you want.
    // but now you need to know how to set the result.

    // the possible results is: valid or invalid
    // to resolve the validation as VALID, you don't need to anything.

    // to resolve the validation as INVALID, you need to use the
    // "registerErrors" helper from ctx.

    // the registerErrors require 1 argument, an object.
    // inside this object, you can put anything you want.
    // it will be registered as errors inside the current path.
    ctx.registerErrors({
      foo: {
        message: 'my message here',
        value
      }
    })

    return {
      // handled: true => stop, it's handled
      // handled: false => continue to the next middleware
      handled: true
    }
  }
}

After this, you can register your middleware:

const { registerMiddleware } = require('jzor')

registerMiddleware(allowMiddleware)