Why can't I redefine a property in a Javascript object?

Question

I am creating a object using Object.create and I want to add properties to it.

> var o = Object.create({});
undefined

> Object.defineProp         


        

Answer 1

Only when both writable and configurable are false, "Cannot redefine property" will happen.

If writable or configurable is true, the error will disappear.

"use strict"

var obj = {};

Object.defineProperty(obj, "name",
{
   value: "Fundebug",
   writable: false,
   configurable: false
})

Object.defineProperty(obj, "name",
{
   value: "云麒"
}) // “Uncaught TypeError: Cannot redefine property: name”

Therefore, jdphenix and Jonathan are not exactly correct.