JavaScript 对象作为 object 参考的属性

Question

I want to understand how objects work in JS.

const obj = { inner: { a: 'Hello' } };

const clone = { ...obj };

// obj === clone -> false
// !!! BUT !!!
// obj.inner === clone.inner -> true

clone.inner = { a: 'world' };
// obj === { inner: { a: 'Hello' } }
// clone === { inner: { a: 'World' } }

Is there a documentation on this behaviour? Can I rely on inner objects references equality while creating new object via spread operator?

Answer 1

... spread syntax creates a shallow copy anything deeper then level one will still stays as reference to original object

 const obj = { inner: { a: 'Hello' } }; const clone = {...obj }; console.log(obj === clone) console.log(obj.inner === clone.inner)

Answer 2

Shallow Cloning If the item being spread into the target is an object, only a reference to that object will be copied. The spread operator will not recursively deep clone properties. In addition, only own, enumerable properties are copied.

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