JS object copying (deep copy and shallow copy)

var obj = {a:1,b:2}
undefined
Object.assign({c:3},obj)
{c: 3, a: 1, b: 2}
obj
{a: 1, b: 2} 
Compatibility writing if (Object.assign) {//compatible} else {//incompatible}

var obj1 = { foo: "foo" };
var obj2 = { bar: "bar" };
 
var copySpread = { ...obj1, ...obj2 }; // Object {foo: "foo", bar: "bar"}
copySpread 
{foo: "foo", bar: "bar"}
var obj = {a:1,b:2,c:3}
var objs = {...obj}
objs
{a: 1, b: 2, c: 3}
objs.a=10
10
objs
{a: 10, b: 2, c: 3}
obj
{a: 1, b: 2, c: 3}

var obj = {a:1,b:[1,2,3],c:{e:3},bool:false}
undefined
var objs = JSON.parse(JSON.stringify(obj))
undefined
objs
{a: 1, b: Array(3), c: {…}, bool: false}
objs.bool = true
true
objs
{a: 1, b: Array(3), c: {…}, bool: true}
obj
{a: 1, b: Array(3), c: {…}, bool: false}

function deepClone(obj) {
  var copy;
 
  // If obj is null, undefined or not an object, return obj directly
  // Handle the 3 simple types, and null or undefined
  if (null == obj || "object" != typeof obj) return obj;
 
  // Handle Date
  if (obj instanceof Date) {
    copy = new Date();
    copy.setTime(obj.getTime());
    return copy;
  }
 
  // Handle Array
  if (obj instanceof Array) {
    copy = [];
    for (var i = 0, len = obj.length; i < len; i++) {
        copy[i] = clone(obj[i]);
    }
    return copy;
  }
 
  //Handle Function
  if (obj instanceof Function) {
    copy = function() {
      return obj.apply(this, arguments);
    }
    return copy;
  }
 
  //Handle Object
  if (obj instanceof Object) {
      copy = {};
      for (var attr in obj) {
          if (obj.hasOwnProperty(attr)) copy[attr] = clone(obj[attr]);
      }
      return copy;
  }
 
  throw new Error("Unable to copy obj as type isn't supported " + obj.constructor.name);
}