hasOwnProperty is the fastest!!

obj_copy.benchmark.js

var values = [
  123, // int
  "string", // short string
  true, // boolean
  42.195, // float
  "AAAAAABBCCCCCCDDDDDDDDEEEEEEEAAAAAAAAAAAAA", // string
  null
];

function passObjByValue(N, nkey, keylen) {
  console.log("-- N", N, "nkey", nkey, "keylen", keylen, "--");
  var obj = {}, i;

  var k;
  for (i=0; i<nkey; i++) {
    k = "";
    for (j=i + 0x41; j<keylen+i+0x40; j++) {
      k+= String.fromCharCode(j);
    }
    obj[k] = values[i % values.length];
  }

  var a;
  console.time("JSON");
  for (i=0; i<N; i++) {
    obj.id = i;
    var obj_str = JSON.stringify(obj);
    a = JSON.parse(obj_str);
  }
  console.timeEnd("JSON");


  var b;
  console.time("iterate");
  for (i=0; i<N; i++) {
    b = {};
    Object.keys(obj).forEach(function(k) {
      b[k] = obj[k];
    });
    b.id = i;
  }
  console.timeEnd("iterate");

  var c;
  console.time("reduce");
  for (i=0; i<N; i++) {
    c = Object.keys(obj).reduce(function(o, k) {
      o[k] = obj[k];
      return o;
    }, {id : i});
  }
  console.timeEnd("reduce");

  var d;
  console.time("reduce2");
  var keys = Object.keys(obj); 
  for (i=0; i<N; i++) {
    d = keys.reduce(function(o, k) {
      o[k] = obj[k];
      return o;
    }, {id : i});
  }
  console.timeEnd("reduce2");

  var e;
  console.time("iterate2");
  var keys = Object.keys(obj); 
  for (i=0; i<N; i++) {
    e = {};
    keys.forEach(function(k) {
      e[k] = obj[k];
    });
    e.id = i;
  }
  console.timeEnd("iterate2");

  console.time("hasOwnProperty");
  var g = {};
  for (var attr in obj) {
    if (obj.hasOwnProperty(attr)) g[attr] = obj[attr];
  }
  console.timeEnd("hasOwnProperty");
}

passObjByValue(1000, 4, 4);
passObjByValue(5000, 4, 4);

passObjByValue(10000, 4, 4);
passObjByValue(10000, 4, 10);
passObjByValue(10000, 4, 20);
passObjByValue(10000, 4, 40);

passObjByValue(10000, 4, 4);
passObjByValue(10000, 10, 4);
passObjByValue(10000, 40, 4);
passObjByValue(100000, 40, 4);

-- N 1000 nkey 4 keylen 4 --
JSON: 10ms
iterate: 3ms
reduce: 3ms
reduce2: 1ms
iterate2: 4ms
hasOwnProperty: 0ms
-- N 5000 nkey 4 keylen 4 --
JSON: 24ms
iterate: 9ms
reduce: 8ms
reduce2: 5ms
iterate2: 6ms
hasOwnProperty: 0ms
-- N 10000 nkey 4 keylen 4 --
JSON: 42ms
iterate: 17ms
reduce: 16ms
reduce2: 11ms
iterate2: 13ms
hasOwnProperty: 0ms
-- N 10000 nkey 4 keylen 10 --
JSON: 42ms
iterate: 18ms
reduce: 15ms
reduce2: 10ms
iterate2: 13ms
hasOwnProperty: 0ms
-- N 10000 nkey 4 keylen 20 --
JSON: 43ms
iterate: 16ms
reduce: 16ms
reduce2: 11ms
iterate2: 12ms
hasOwnProperty: 0ms
-- N 10000 nkey 4 keylen 40 --
JSON: 95ms
iterate: 29ms
reduce: 29ms
reduce2: 18ms
iterate2: 20ms
hasOwnProperty: 0ms
-- N 10000 nkey 4 keylen 4 --
JSON: 38ms
iterate: 16ms
reduce: 16ms
reduce2: 11ms
iterate2: 13ms
hasOwnProperty: 0ms
-- N 10000 nkey 10 keylen 4 --
JSON: 85ms
iterate: 36ms
reduce: 37ms
reduce2: 31ms
iterate2: 29ms
hasOwnProperty: 0ms
-- N 10000 nkey 40 keylen 4 --
JSON: 439ms
iterate: 187ms
reduce: 194ms
reduce2: 144ms
iterate2: 142ms
hasOwnProperty: 1ms
-- N 100000 nkey 40 keylen 4 --
JSON: 4433ms
iterate: 1886ms
reduce: 1882ms
reduce2: 1429ms
iterate2: 1440ms
hasOwnProperty: 1ms