Object in ES-5

ES5 adds more features to Object.

Object.preventExtensions(obj) makes it impossible to add properties to obj. You can still change and delete properties. 
Object.isExtensible(obj) is to check whether obj is extensible.

Object.seal(obj) prevents extensions and makes all properties “unconfigurable”. The latter means that the attributes of properties can’t be changed, any more. Read-only properties stay read-only, enumerable properties stay enumerable, etc. But You can still change the property.
Object.isSealed(obj) is to check whether obj is sealed.

Object.getOwnPropertyDescriptor(obj, 'foo')
Object.defineProperty(obj, 'foo', { enumerable: false });

Object.freeze(obj) makes all properties non-writable and seals obj. 
Object.isFrozen(obj) is to check whether obj is frozen.

Reference:
http://ejohn.org/blog/ecmascript-5-objects-and-properties/
http://kangax.github.io/es5-compat-table/