deep-copy javascript json

javascript deep copy using JSON

I have problem with javascript object(array) deep copy. I read many good way to deal with it. And I also know that jQuery has $.extend API to this problem. But my question is: Can I just using JSON stringify and parse method to solve this problem?

Here’s my code:

function deepCopy(oldValue) { 
var newValue
strValue = JSON.stringify(oldValue)
return newValue = JSON.parse(strValue)
var a = {
b: 'b',
c: [1,2,4],
d: null
copy = deepCopy(a)
console.log(a === copy) // false
console.log(a.c === copy.c) // false

PS: I’ve known that if no all objects are serializable, but the only situation I know is that when the object contains a property which is function. Any other situation?

If your object is “small” and contains exclusively serializable properties, a simple deepCopy hack using JSON serialization should be OK. But, if your object is large, you could run into problems. And if it contains unserializable properties, those’ll go missing:

var o = {
a: 1,
b: 2,
sum: function() { return a + b; }
var o2 = JSON.parse(JSON.stringify(o));


Object {a: 1, b: 2}

Interestingly enough, a fair number of deep-copy solutions in C# are similar serialization/deserialization tricks.

Addendum: Not sure what you’re hoping for in terms of comparing the objects after the copy. But, for complex objects, you generally need to write your own Compare() and/or Equals() method for an accurate comparison.

Also notable, this sort of copy doesn’t preserve type information.

JSON.parse(JSON.stringify(new A())) instanceof A === false