如何深度复制包含集合的JavaScript对象

Question

jQuery deep copy using
var objCopy = jQuery.extend(true, {}, obj);

works well for
var obj = {str: "text", num: 2, arr: [1, 2, 3]}

but what about for
var obj = {str: "text", num: 2, set: new Set([1,2,3])} ?

I've found that making changes to obj.set also changes objCopy.set .
Is there a way to drill down to the set inside obj and assign a deep copy of that to objCopy ?

Answer 1

You can implement a small copy function that will handle it when there is a set.

function myCopy(obj) {
  obj = jQueryDeepCopierOfObject(obj); // Deep copy it here

  for (let prop in obj)
    if (obj.hasOwnProperty(prop))
      if (Set.prototype.isPrototypeOf(obj[prop]))
        obj[prop] = new Set(obj[prop]);

  // hoping there won't be any object in the set.
  return obj;
}

EXAMPLE:

 var a = { a: "foo", b: "bar", c: "baz", set: new Set() }; a.set.add("fox"); a.set.add("bat"); a.set.add("wisdom"); var b = mycopy(a); console.log("a === b: ", a === b); // → false console.log("a.set === b.set: ", a.set === b.set); // → false b.set.add("kindness"); console.log("set a has kindness: ", a.set.has("kindness")); // → false console.log("set b has kindness: ", b.set.has("kindness")); // → true function mycopy(obj) { obj = Object.assign({}, obj); for (let prop in obj) if (obj.hasOwnProperty(prop)) if (Set.prototype.isPrototypeOf(obj[prop])) obj[prop] = new Set(obj[prop]); return obj; }