object Object.defineProperty()执行后不显示新增属性

Question

 var obj = { name: "dev", age: 27, } obj = Object.defineProperty(obj, 'mail', { value: 'dev@hmail.com', writable: true }); console.log(obj) // Printing the object with old properties ie.{ name: 'dev', age: 27 }}

With the above code it is showing only the old properties. Why does it not showing the new property "mail"?

Answer 1

In the documentation for Object.defineProperty it is said

By default, values added using Object.defineProperty() are immutable and not enumerable .

If you print an object with console.log(obj) though, there might be the possibility, that only the enumerable properties are printed (depends on the implementation of console.log). The defined member is still there, but just does not show up.

Printing the member directly works:

 var obj = { name: "dev", age: 27, }; obj = Object.defineProperty(obj, 'mail', { value: 'dev@hmail.com', writable: true }); console.log(obj.mail);