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
| 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 |