Representing logic as data in JSON

Question

For business reasons we need to externalize some conditional logic into external files: preferably JSON.

A simple filter-by scenario could be handled by adding a node a

Answer 1

Please check out (JSL)[https://www.npmjs.com/package/lib-jsl ]. It seems to fit the description given.

Here is a sample :

var JSL = require('lib-jsl');

var bugs = [
    [{ bug : { desc: 'this is bug1 open', status : 'open' } }],
    [{ bug : { desc: 'this is bug2 resolved', status : 'resolved' } }],
    [{ bug : { desc: 'this is bug3 closed' , status : 'closed' } }],
    [{ bug : { desc: 'this is bug4 open', status : 'open' } }],
    [{ bug : { desc: 'this is bug5 resolved', status : 'resolved' } }],
    [{ bug : { desc: 'this is bug6 open', status : 'open' } }],

    [   { workInProgress : '$bug'},
        { bug : '$bug'},
        { $or : [
            { $bind : [ '$bug', { status : 'open'} ] },
            { $bind : [ '$bug', { status : 'resolved'} ] }
        ] }
    ]
];
var query = [{workInProgress : '$wip'}]
var transform = '$wip'
var jsl = new JSL ({
    rules : bugs,
    query : query,
    transform : transform
});
var retval = jsl.run();
console.log(JSON.stringify(retval, null,2));

The response is :

[
  {
    "desc": "this is bug1 open",
    "status": "open"
  },
  {
    "desc": "this is bug2 resolved",
    "status": "resolved"
  },
  {
    "desc": "this is bug4 open",
    "status": "open"
  },
  {
    "desc": "this is bug5 resolved",
    "status": "resolved"
  },
  {
    "desc": "this is bug6 open",
    "status": "open"
  }
]

The main work is done by the query defined in the rule workInProgress :

[   { workInProgress : '$bug'},
    { bug : '$bug'},
    { $or : [
        { $bind : [ '$bug', { status : 'open'} ] },
        { $bind : [ '$bug', { status : 'resolved'} ] }
    ] }
]

This rule can be read as :

To satisfy the query with workInProgress, we define a variable {workInProgress : '$bug'}, which we then proceed to match against all bugs in the database using the next part of the rule {bug : '$bug'}. This part matches all bugs since the shape of the object (it's keys: 'bug') matches the bug records in the database. The rule further asks the $bug variable to be $bind(ed) against patterns containing relevant status values (open and closed) within a $or. Only those bug records whose status value in $bug satisfies all parts of the rule's body qualify for the result.

The result is finally transformed using the transform specification : transform : '$wip' which literally asks for an array of all values returned in the $wip variable of the query.