@riddler/predicator

Predicator

Predicator is a safe (does not eval code), admin or business user facing predicate engine. It turns a string predicate like "score > 600 or (score > 580 and monthly_income > 9000)" along with a supplied context into a true or false. This predicate can be stored as an attribute of a model (ex: an Offer model could store a predicate indicating if it is available to a customer).

Usage

Simple usage:

const Predicator = require('predicator');

// Compile a list of instructions which a Predicator Evaluator can execute

Predicator.compile('score >= 600 or (score > 580 and income > 9000)');

//  [
//    [ 'load', 'score' ],
//    [ 'to_int' ],
//    [ 'lit', 600 ],
//    [ 'compare', 'GTE' ],
//    [ 'jtrue', 11 ],
//    [ 'load', 'score' ],
//    [ 'to_int' ],
//    [ 'lit', 580 ],
//    [ 'compare', 'GT' ],
//    [ 'jfalse', 5 ],
//    [ 'load', 'income' ],
//    [ 'to_int' ],
//    [ 'lit', 9000 ],
//    [ 'compare', 'GT' ]
//  ]


// Evaluation

Predicator.evaluate('score >= 600 or (score > 580 and income > 9000)', {score: 600}); // true

Predicator.evaluate('score >= 600 or (score > 580 and income > 9000)', {score: 590}); // false

Predicator.evaluate('score >= 600 or (score > 580 and income > 9000)', {score: 590, income: 10000}); // true

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/riddler/predicator-js. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The library is available as open source under the terms of the MIT License.