Getting and Setting Property Descriptors in JavaScript (Part 2)

In the previous post, I discussed how to get property descriptors. Now, I am going to tell you how to define a property with a desired property descriptor.

But first, let's see why we would want to do this. Defining properties with property descriptors lets you fine-tune the attributes of the property:

• You can define the enumerability of the property. If the property is enumerable, it will be listed in a for .. in loop or other iteration mechanisms, such as Object.keys. (I don't mean to say the for .. in loop and Object.keys return the same set of properties. No, they have an important difference. The for .. in loop iterates over all properties, whether own or inherited, while Object.keys returns only own properties.)
• If a property is configurable, you can change its definition or even delete it. Otherwise, these actions are not possible.
• For data properties, the writable attribute determines if a value can be assigned to the property. If this flag is set to false, assigning a value to the property will have no effect.
• For accessor properties, get and set attributes determine whether the property is readable and writable, respectively.

Defining properties is carried out with Object.defineProperty and Object.defineProperties functions which will be presented in the next post.

Related Posts

• Object Creation and Manipulation Functions in JavaScript
• Property Descriptors in JavaScript
• Getting and Setting Property Descriptors in JavaScript (Part 1)