The JsonLogic format is designed to allow you to share rules (logic) between front-end and back-end code (regardless of language difference), even to store logic along with a record in a database. JsonLogic is documented extensively at JsonLogic.com, including examples of every supported operation and a place to try out rules in your browser.
The same format can also be executed in PHP by the library json-logic-php
bower install --save json-logic-js
npm install json-logic-js
Note that this project uses a module loader that also makes it suitable for RequireJS projects.
If that doesn't suit you, and you want to manage updates yourself, the entire library is self-contained in
logic.js and you can download it straight into your project as you see fit.
curl -O https://raw.githubusercontent.com/jwadhams/json-logic-js/master/logic.js
This is a simple test, equivalent to
1 == 1. A few things about the format:
- The operator is always in the "key" position. There is only one key per JsonLogic rule.
- The values are typically an array.
- Each value can be a string, number, boolean, array (non-associative), or null
Here we're beginning to nest rules.
3 > 1 && 1 < 3
Obviously these rules aren't very interesting if they can only take static literal data. Typically
jsonLogic will be called with a rule object and a data object. You can use the
var operator to get attributes of the data object:
If you like, we support syntactic sugar on unary operators to skip the array around values:
You can also use the
var operator to access an array by numeric index:
Here's a complex rule that mixes literals and data. The pie isn't ready to eat unless it's cooler than 110 degrees, and filled with apples.
var rules = "and" :"<" : "var" : "temp" 110"==" : "var" : "pie.filling" "apple";var data = "temp" : 100 "pie" : "filling" : "apple" ;jsonLogic;// true
Always and Never
Sometimes the rule you want to process is "Always" or "Never." If the first parameter passed to
jsonLogic is a non-object, non-associative-array, it is returned immediately.
//AlwaysjsonLogic;// true//NeverjsonLogic;// false
This library makes use of
Array.reduce, so it's not exactly Internet Explorer 8 friendly.
It's not possible to include everyone's excellent ideas without the core library bloating, bringing in a ton of outside dependencies, or occasionally causing use case conflicts (some people need to safely execute untrusted rules, some people need to change outside state).