mapping-size-calc.js

var JSONPath = require('JSONPath');

const doc = require('./mapping.json');
const mappings = JSONPath({json: doc, path: "$['serilog-2017.05'].mappings.*", resultType: "all" });

function countProps(obj) {
   var result = 0;
   if (obj) {
      Object.getOwnPropertyNames(obj).forEach(function(p) {
        result += 1 + countProps(obj[p].properties);
      });
   }
   return result;
}

var result = mappings.map(function(mapping) {
  return {name:mapping.parentProperty, count:countProps(mapping.value.properties)};
});

result.sort(function(a,b) {
  return b.count - a.count;
});

console.log(JSON.stringify(result, null, 4));