json-evaluator

The aim of the json is to produce a boolean

Installation

Yarn

yarn add json-evaluator

NPM

npm i json-evaluator

Usage

Import the package

import evaluator from 'json-evaluator'

Validate the JSON instance

evaluator.validator.validate(instance, {})

• instance is a JSON object

Evaluate the JSON instance

evaluator.evaluate(JSON.parse(instance), {})

How does the JSON work ?

The json needs 3 properties:

• a value to compare
• a value to compare to
• an operator

{
    "compare": {},
    "compareTo": {},
    "operator": ""
}

A value is defined by two properties:

• The type of the value
• The value itself

{
    "type": "",
    "value: "",
}

Obviously:

• the type and the value have to match
• the operator has to be one of the allowed as well

Allowed types are:

• string
• number
• boolean
• expression
• field

An expression is simply another node to compare, the value is thus the object you want to evaluate.

A field can be used to give an external value. External values can be given through a dictionnary. The value will then be the dictionnary key that holds the value.

Allowed operators are:

• >
• <=
• >
• >=
• ==
• !=
• ||
• &&
• or
• and

They obviously can't be applied to all types.

Examples

Not all operators match

Bad

{
  "compare": {
    "type": "string",
    "value": "olivier"
  },
  "compareTo": {
    "type": "string",
    "value": "arnaud"
  },
  "operator": ">="
}

This will produce an error

Good

{
  "compare": {
    "type": "string",
    "value": "olivier"
  },
  "compareTo": {
    "type": "string",
    "value": "arnaud"
  },
  "operator": "=="
}

This will produce false

Type and value have to match

Bad

{
  "compare": {
    "type": "string",
    "value": 14
  }
}

Good

{
  "compare": {
    "type": "number",
    "value": 14
  }
}

"Expression" type

{
  "compare": {
    "type": "expression",
    "value": {
      "compare": {
        "type": "string",
        "value": "olivier"
      },
      "compareTo": {
        "type": "string",
        "value": "arnaud"
      },
      "operator": "=="
    }
  },
  "compareTo": {
    "type": "boolean",
    "value": true
  },
  "operator": "&&"
}

This will produce (bool) false because:

• "olivier" == "arnaud" is false
• true && false is false

Misc

Run de tests

yarn test tests/

Generate dist files

./node_modules/.bin/babel lib/ --out-dir dist/