dsl.js

'use strict';

const R = require('ramda');

const rules = {"&": [
    {">": [ "!products.blah", 2 ]},
    {">": [ "!products.meow", 1 ]}
]};

const basket = { products: { meow: 2, blah: 3 } };

const Functions = {
    "&": (o1, o2) => o1 && o2,
    ">": (o1, o2) => o1 > o2
};

let runDSL = (Func, Obj) => {
    const operation = Object.keys(Func)[0];
    const operands = Func[operation];

    const args = operands.map((o) => {
      const t = typeof o;

      if (t == 'object') {
        return runDSL(o, Obj);
      }
      else if (/^!/.exec(o)) {
        const objLens = R.lensPath(o.slice(1).split('.'));
        return R.view(objLens, Obj);
      }
      else return o;
    });

    console.log(operation, args);
    return Functions[operation].apply(null, args);
};

const output = runDSL(rules, basket);

console.log(output);

/* Outputs:
* > [ 3, 2 ]
* > [ 2, 1 ]
* & [ true, true ]
* true
*/