prupp.js

var 
	deepExtend = require('deep-extend'),
	deepmerge = require('deepmerge'),
	klon = require('klon'),
  jonas = (function () {
      const toString = Object.prototype.toString;

      function isMergeable (value) {
          return value && typeof value === 'object' && toString.call(value) !== '[object Date]' && toString.call(value) !== '[object RegExp]';
      }

      return function merge (obj1, obj2) {
          var out = {}, key, p1, p2;

          for (key in obj2) {
              p1 = obj1[key];
              p2 = obj2[key];

              if (!isMergeable(p2)) {
                  out[key] = p2;
              } else {
                  if (isMergeable(p1)) {
                      out[key] = merge({}, p1);
                  } else {
                      out[key] = {};
                  }

                  out[key] = merge(out[key], p2);
              }
          }

          return out;
      };
  }());


var obj1 = {
   b:{a:1,b:2},
   d:1,
   e:2,
   f:3
};
var obj2 = {
   a:1,
   b: {a:1},
   c:3,
   d: {
      a:1,
      b:2,
      c:3,
      d: {
         a:1,
         b:2,
         c:3,
         d: {
             a:1,
             b:2,
             c:3,
             d: {
                a:1,
                b:2,
                c:3,
                d: {
                   a:1,
                   b:2,
                   c:3
                }
             }  
          }  
      }
   },
   h: new Date()
};
var n, obj3;
console.log()
console.log('---');
console.log('50000 iterations of');
console.log('---');
console.time('deepExtend'); n=50000;while(--n) obj3 = deepExtend({},obj1,obj2); console.timeEnd('deepExtend');
console.time('jonas'); n=50000;while(--n) obj3 = jonas(obj1,obj2); console.timeEnd('jonas');
console.time('deepmerge.all'); n=50000;while(--n) obj3 = deepmerge.all([obj1,obj2]); console.timeEnd('deepmerge.all');
console.time('klon'); n=50000;while(--n) obj3 = klon(obj2,klon(obj1)); console.timeEnd('klon');
console.time('Object.assign'); n=50000;while(--n) obj3 = Object.assign({},obj1,obj2); console.timeEnd('Object.assign');
console.time('Spread'); n=50000;while(--n) obj3 = {...obj1,...obj2}; console.timeEnd('Spread');

console.log('---');
console.log('---');
console.log('klon (deep)');
console.log(klon(obj2,klon(obj1)));
console.log('jonas (deep)');
console.log(jonas(obj1,obj2));
console.log('deepmerge.all (deep)');
console.log(deepmerge.all([obj1,obj2]));
console.log('deepExtend (deep)');
console.log(deepExtend({},obj1,obj2));
console.log('Object.assign (shallow)');
console.log(Object.assign({},obj1,obj2));
console.log('Spread (shallow)');
console.log({...obj1,...obj2});