Run results for: Spread vs object.assing vs forEach

Test name	Executions per second
Spread	5805208.0 Ops/sec
Object.assign	4032086.8 Ops/sec
Foreach	1351589.6 Ops/sec

Spread

const a = {
    email: "abc@mail.com",
    phone: "12345678",
};

const b = {
    app_version: "AP.12",
    appsflyer_id: "askldjajkshdlkjh2323h4234j2l3j4h",
    advertising_id: "23;o4h2l34hl2kj3h4kj23h4",
    device_os_version: "12",
    device_name: "Aifon 15 PRO",
    firebase_instance_id: "2liu3hiuo23y4u23y4ui2y34iy3u4y234",
};

const res = {
    email: null,
    phone: null,
    last_name: null,
    first_name: null,
    app_version: null,
    appsflyer_id: null,
    advertising_id: null,
    device_os_version: null,
    device_name: null,
    firebase_instance_id: null,
    ...a,
    ...b
};

Object.assign

const a = {
    email: "abc@mail.com",
    phone: "12345678",
};

const b = {
    app_version: "AP.12",
    appsflyer_id: "askldjajkshdlkjh2323h4234j2l3j4h",
    advertising_id: "23;o4h2l34hl2kj3h4kj23h4",
    device_os_version: "12",
    device_name: "Aifon 15 PRO",
    firebase_instance_id: "2liu3hiuo23y4u23y4ui2y34iy3u4y234",
};

const res = Object.assign({
      email: null,
      phone: null,
      last_name: null,
      first_name: null,
      app_version: null,
      appsflyer_id: null,
      advertising_id: null,
      device_os_version: null,
      device_name: null,
      firebase_instance_id: null
    }, 
    a, 
    b);

Foreach

const a = {
      email: "abc@mail.com",
      phone: "12345678",
      last_name: "Last Name",
      first_name: "First Name",
      app_version: null,
      appsflyer_id: null,
      advertising_id: null,
      device_os_version: null,
      device_name: null,
      firebase_instance_id: null
};

const b = {
    app_version: "AP.12",
    appsflyer_id: "askldjajkshdlkjh2323h4234j2l3j4h",
    advertising_id: "23;o4h2l34hl2kj3h4kj23h4",
    device_os_version: "12",
    device_name: "Aifon 15 PRO",
    firebase_instance_id: "2liu3hiuo23y4u23y4ui2y34iy3u4y234",
};

const res = {
      email: null,
      phone: null,
      last_name: null,
      first_name: null,
      app_version: null,
      appsflyer_id: null,
      advertising_id: null,
      device_os_version: null,
      device_name: null,
      firebase_instance_id: null
};

Object.keys(a).forEach(key => {
    res[key] = a[key];
  });
Object.keys(b).forEach(key => {
    res[key] = b[key];
  });