@rule.js/expression

Rule.js: Expression Language

A simple language for expressing business rules.

API

This module exports a single function. The function accepts an optional constructor for the @rule.js/core module.

Example:

const Rule = require('@rule.js/core').extend({}, {
	elasticsearch: require('@rule.js/elasticsearch')
})
const ruleExpression = require('@rule.js/expression')(Rule)

const rule = ruleExpression('"name" equal "sample"')
const query = rule.elasticsearch()

// query:
// {
//   "bool": {
//     "must": [
//       {
//         "term": {
//           "name": "sample"
//         }
//       }
//     ]
//   }
// }

Language

The language is meant to be easy enough for non-programmers to pick up. There are no functions or other more complex constructs.

Literals

There are currently only two types of literals: strings and booleans. Strings must always be double quoted. To place a double quote inside of a string, an escape sequence must be used (\").

Valid:

"hello"
"this is \"a quote\""
"this is a backslash: \\"

Invalid:

'single quotes'
"hello "quotes""

Comparison Operators

`equal`

Tests if the key is equal to the given property.

Example:

"enabled" equal true

`not equal`

Compares if the key is not equal to the given property.

Example:

"status" not equal "disabled"

`is empty`

Tests if the given key is empty.

Example:

"quantity" is empty

`is not empty`

Inversion of the is empty operator.

Example:

"quantity" is not empty

`any`

Tests if the key is equal any of the given values.

Example:

"status" any ("open", "draft")

`not any`

Test if the given key is not equal any of the specified values.

Example:

"status" not any ("pending", "new")

`contains`

Test if the key contains the given value.

Example:

"hobbies" contains "Guitar"

`not contains`

Inverse of the contains operator.

Example:

"hobbies" not contains "Guitar"

`greater than`

Test if the key is less than the specified value.

Example:

"age" less than 21

`less than`

Test if the key is greater than the specified value.

Example:

"income" greater than 55374.19

Logical Operators

`and`

Combines two rules together. If one of them is false, the result from the operator will be false.

Example:

"quantity" is not empty and "status" not equal "disabled"

`or`

Combines two rules togther. If one of them is truthful, the result from the operator will be true.

Example:

"quantity" is empty or "status" equal "disabled"

You can mix logical operators together. For example:

"quantity" is empty or "status" is empty and "owner" is empty

Keys

You can do deep lookups with the following:

"person"."name" equal "Rick"

@rule.js/expression