Save json objects compactly in memory. Save just unique key names and values

json_arch.js

'use strict';

class JsonArch
{
    constructor(){
        this.storage = {keys: [], values: {}};
        this.objs = [];
    }

    add_recursive(obj, storage){
        let o = {};
        let idx, mkey;
        Object.keys(obj).forEach(key=>{
            if ((idx=this.storage.keys.indexOf(key)) === -1)
                this.storage.keys.push(key);
            mkey = idx === -1 ? this.storage.keys.length-1 : idx;
            if (!storage[mkey])
                storage[mkey] = [];
            if (obj[key] == null || typeof obj[key] !== 'object')
            {
                if ((idx=storage[mkey].indexOf(obj[key])) === -1)
                    storage[mkey].push(obj[key]);
                    o[mkey] = idx === -1 ? storage[mkey].length-1 : idx;
            }
            else
                o[mkey] = this.add_recursive(obj[key], storage[mkey]);
        });
        return o;
    }

    add(obj){
        this.objs.push(this.add_recursive(obj, this.storage.values));
    }

    extract_recursive(obj, storage){
        let o = {};
        Object.keys(obj).forEach(key=>{
            if (typeof obj[key] !== 'object')
                o[this.storage.keys[key]] = storage[key][obj[key]];
            else
                o[this.storage.keys[key]] = this.extract_recursive(obj[key],
                    storage[key]);
        });
        return o;
    }

    extract(){
        let objs = [];
        this.objs.forEach(o=>{
            objs.push(this.extract_recursive(o, this.storage.values));
        });
        return objs;
    }
}

module.exports = JsonArch;