Question

While reading a book of JavaScript I read that

all the attributes of Data Properties defaults to true when “defined directly on an object”.

then after some description it again says that

“When you are using Object.defineProperty()”, the values for configurable, enumerable, and
writable default to false unless otherwise specified.

I guess, in first statement “defined directly on an object” means using dot operator or by object literal notation like this:

var obj = new Object();
obj.name = "Mahesh";

But is there any way to experiment to check what these attributes have been set to, after the property has been added to the object by either method?

Answer 1

You can use getOwnPropertyDescriptor:

> var desc = Object.getOwnPropertyDescriptor(obj, 'name');
{"value":"Mahesh","writable":true,"enumerable":true,"configurable":true}

desc will contain the the flags configurable and enumerable. If the property is a data descriptor (no get or set), desc will also contain value and the flag writable. If the property is an accessor descriptor, desc will also contain the get and set methods.