JS object copy (deep and shallow copy)

1. Light copy

1、(target,source,source...)

a. Can support multiple object copying

b. If the source and target attributes are the same source will copy the target attributes.

c. Target can only be an Object object object

var obj = {a:1,b:2}
undefined
({c:3},obj)
{c: 3, a: 1, b: 2}
obj
{a: 1, b: 2} 
Compatibility writingif(){//compatible}else{//不compatible}

2. Expansion operator (spread)

Supports copying multiple objects to one object "

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}
=10
10
objs
{a: 10, b: 2, c: 3}
obj
{a: 1, b: 2, c: 3}

2. Deep copy

1. Use object serialization () and ()

Note: This method is only valid if the original object contains a serializable value type and does not have any circular references. An example of a non-serialized value type is a Date object - it can only be parsed into a string and cannot be parsed back to its original Date object or the property value in the object is function

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

2. Use recursion to judge object properties

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();
    (());
    return copy;
  }
 
  // Handle Array
  if (obj instanceof Array) {
    copy = [];
    for (var i = 0, len = ; i &lt; len; i++) {
        copy[i] = clone(obj[i]);
    }
    return copy;
  }
 
  // Handle Function
  if (obj instanceof Function) {
    copy = function() {
      return (this, arguments);
    }
    return copy;
  }
 
  // Handle Object
  if (obj instanceof Object) {
      copy = {};
      for (var attr in obj) {
          if ((attr)) copy[attr] = clone(obj[attr]);
      }
      return copy;
  }
 
  throw new Error("Unable to copy obj as type isn't supported " + );
}

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