Remove all empty properties from an object, recursively.

clean.js

const sample = {
  a: 'Hello',
  b: '', // Will be removed
  c: null,
  d: {
    a: 1,
    b: '', // Will be removed
    c: 3,
    d: {
      a: 1,
      b: '', // Will be removed
      c: 'world'
    },
    e: null
  }
}

/**
 * Attach the cleaning method to the object's prototype chain.
 */
Object.defineProperties(Object.prototype, {
  clean: {
    configurable: true,
    enumerable: false,
    value: function clean (obj = this) {
      Object.keys(obj).forEach(key => obj[key] !== null && typeof obj[key] === 'object' ? clean(obj[key]) :
        obj[key] === '' && delete obj[key]);

      return obj;
    }
  }
});

const cleanObject = sample.clean();
console.log(JSON.stringify(cleanObject, null, 2));