antonpolyakin / json-conditions

Simple conditional logic to evaluate against javascript objects

Simple conditional logic testing of JSON objects

Simple json takes an array of conditions that can be compared against a JSON object to test if that object passes or fails the conditions.

Quickstart

npm install json-conditions

const checkConditions = require('json-conditions');

const reference = {
	user: {
		preferredName: 'Alex',
		age: 4,
	},
	toy: {
		name: 'Model Train',
		tracks: 18,
		engines: 1
		battery: true,
	}
};

const simpleRules = [
	{ property: 'toy.engines', op: 'gt', value: 2 },
	{ property: 'batteries', op: 'eq', value: true },
];

// Returns true
checkConditions({
	rules: simpleRules,
	satisfy: 'ANY',
	log: console.log,
}, reference);

// Returns false
checkConditions({
	rules: simpleRules,
	satisfy: 'ALL',
	log: console.log,
}, reference);

// Returns true
checkConditions({
	rules: [
		// A required condition must always be satisfied regardless of the value
		{ property: 'toy.tracks', op: 'gt', value: 2, required: true },
		{ property: 'batteries', op: 'eq', value: true },
		{ property: 'solarPanels', op: 'gte', value: 0 },
	],
	satisfy: 'ANY',
	log: console.log,
}, reference);

Parameters

Param	Type	Default	Description
settings.log	function		Optional function to log debug output from the evaluation
settings.rules	object[]		Rules, see below
settings.satisfy	string	ANY	How many rules must be satisfied to pass, 'ALL' or 'ANY'
reference	object		The javascript object to evaluate the rules against

Rules

Each rule is described by an object with the following properties

property	Type	Default	Description
op	string		The logical operator to use for comparison (see below)
property	string		The property in the reference object to check, evaluated by
required	boolean	false	If true, this rule must always evaluate to true for the object to pass the conditions
value	*		Value to compare the property to

Property is passed to lodash.get to lookup the value in the object. So effectively the rules are evaluated to get(reference, rule.property) ${rule.op} ${rule.value}

Operators

The following operators can be used in rules. Operators use javascript coersion (ie == not ===) Additionally, we assume that rule values may have come from a form, and so try to be forgiving when dealing with booleans. If the value of the property is a boolean, then the strings 'true' and 'false' (case insensitive) will be converted to booleans.

Operator	Javascript operation	Notes
eq	==
neq	!=
ne	!=	(Alias for neq)
gt	>
gte	>=
lt	<
lte	<=
absent	!
empty	!	(Alias for absent)
present	!!
startsWith	_.toString(x).startsWith()
endsWith	_.toString(x).endsWith()
contains	_.toString(x).includes()

License

Licensed under the NoHarm license