Abstract

Provides a JSON based term evaluator to calculate decisions based on configuration files The syntax of the JSON-terms is derived from Lisp .

Contents

• Meta
• Class Decision
  • Parameters
  • Methods
    • _ISOStringToDate
    • eval
    • on
• Class EvalResult
  • Parameters
  • Members

Meta

| | | | --- | --- | | File | decision.js | | Abstract | Provides a JSON based term evaluator to calculate decisions based on configuration files The syntax of the JSON-terms is derived from Lisp . | | Author | Volker Böhm | | Copyright | Copyright ( c ) 2020 Volker Böhm | | License | This software is licensed under the GNU LESSER GENERAL PUBLIC LICENSE Version 3 . It is furnished "as is" , without any support , and with no warranty , express or implied , as to its usefulness for any purpose . |

Class Decision

new Decision(variables)

Creates a value class providing the ability to evalutate a json based value . Additionally it explains the value in a juman readable string . Supported operations are

• [ "or" , t1 , t2 , . . . ]
• [ "and" , t1 , t2 , . . . ]
• [ operator , t1 , t2 ] with operators '>' , '<' , '> = ' , '< = ' , ' ! = ' , ' = '
• [ "+/-" , t1 , t2 ]
• [ "if" , t1 , then , else ]
• [ "switch" , t1 , { map } ] where map is an array of variable value maps . Example [ "switch" , 1 , { 1 : "a" , 2 : "b" } ] results in 'a'
• [ "function" , . . . parameter ] where function is registrated by a call to 'on'

Example

const variables = {
   'a/b': 1,
   'b/c': 2,
   'system/presence': 'awake'
}
const value = new Decision(variables)
const result = value.decide(
     [
          'and',
          ['or', ['<', 'a/b', 10], ['<', 'b/c', 2]],
          ['or', ['>=', 'a/b', 10], ['>=', 'b/c', 2]]
      ]
)
// returns result.value = true and result.reason = 'a/b (1) is < 10 and b/c (2) is >= 2'

Decision Parameters

| Name | Type | Attribute | Default | Description | | ---------- | ------------ | ------------ | ------------ | ----------------- | | variables | Object | optional | { } | list of known variables and values | |

Decision Methods

_ISOStringToDate

_ISOStringToDate (value) => {Date, any}

Converts any value from an ISO formatted date string to a date object If it is not an ISO formatted date string , the original value will be returned

_ISOStringToDate Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | value | any | any value | |

_ISOStringToDate returns

| Type | Description | | ---- | ----------- | | Date, any | a Date object or the original value |

eval

eval (jsonTree) => {EvalResult}

Calculates a value based on a json based json tree

eval Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | jsonTree | Object | json structured boolean logic | |

eval throws

| Type | Description | | ---- | ----------- | | Error | on any error in the jsonTree |

eval returns

| Type | Description | | ---- | ----------- | | EvalResult | result of the evaluation |

on

on (event, callback)

Sets a callback .

on Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | event | string | event name ( not case sensitive ) for the callback | | | callback | function | ( parameter ) | |

on throws

| Type | Description | | ---- | ----------- | | Error | if the callback is not 'function' |

Class EvalResult

new EvalResult(value, reason)

Creates a result object with a "value" and a "reason" and a list of used variable : value pairs

EvalResult Parameters

| Name | Type | Description | | ---------- | ------------ | ----------------- | | value | Date, string, number, boolean | evaluation value | | | reason | string | value reason in human readable form | |

EvalResult Members

| Name | Type | description | | ------------ | ------------ | ------------ | | reason | string | Reason explaining the result | | value | Date, string, number, boolean | Value of the result | | variables | Array.<string> | List of missing variables found |