This set of Javascript Multiple Choice Questions & Answers (MCQs) focuses on “Object Attributes and Serialization”.
1. The unordered collection of properties, each of which has a name and a value is called
a) String
b) Object
c) Serialized Object
d) All of the mentioned
View Answer
Explanation: An object is an unordered collection of properties, each of which has a name and a value. Property names are strings, so we can say that objects map strings to values.
2. The object has three object attributes namely
a) Class, parameters, object’s extensible flag
b) Prototype, class, objects’ parameters
c) Prototype, class, object’s extensible flag
d) Native object, Classes and Interfacces and Object’s extensible flag
View Answer
Explanation: Every object has three associated object attributes :
- An object’s prototype is a reference to another object from which properties are inherited.
- An object’s class is a string that caegorizes the type of an object.
- An object’s extensible flag specifies whether new properties may be added to the object.
3. Consider the following code snippet :
var book = { "main title": "JavaScript", 'sub-title': "The Definitive Guide", "for": "all audiences", author: { firstname: "David", surname: "Flanagan" } };
In the above snippet, firstname and surname are
a) properties
b) property values
c) property names
d) objects
View Answer
Explanation: firstname and surname are the property names. The value of that particular property is itself an object. That is why these property names are unquoted.
4. A linkage of series of prototype objects is called as :
a) prototype stack
b) prototype chain
c) prototype class
d) prototypes
View Answer
Explanation: Consider an example, Date.prototype inherits properties from Object.prototype, so a Date object created by new Date() inherits properties from both Date.prototype and Object.prototype. This linked series of prototype objects is known as prototype chain.
5. Consider the below given syntax
book[datatype]=assignment_value;
In the above syntax, the datatype within the square brackets must be
a) An integer
b) A String
c) An object
d) None of the mentioned
View Answer
Explanation: When using square bracket notation, the expression inside the square brackets must evaluate to a sting or a value that can be converted to a string.
6. To determine whether one object is the prototype of (or is part of the prototype chain of) another object, one should use the
a) isPrototypeOf() method
b) equals() method
c) === operator
d) none of the mentioned
View Answer
Explanation: To determine whether one object is the prototype of (or is part of the prototype chain of) another object, one should use the isPrototype() method. To find out if p is the prototype of o write p.isPrototypeOf(o).
7. Consider the following code snippet
function f() {};
The above prototype represents a
a) Function f
b) A custom constructor
c) Prototype of a function
d) Not valid
View Answer
Explanation: The above code snippet defines a custom constructor.
8. The purpose of extensible attribute is to
a) make all of the own properties of that object nonconfigurable
b) to configure and bring a writable property
c) “lock down” objects into a known state and prevent outside tampering
d) all of the mentioned
View Answer
Explanation: The purpose of the extensible attribute is to be able to “lock down” objects into a known state and prevent outside tampering.
9. Identify the process done in the below code snippet
o = {x:1, y:{z:[false,null,""]}}; s = JSON.stringify(o); p = JSON.parse(s);
a) Object Encapsulation
b) Object Serialization
c) Object Abstraction
d) Object Encoding
View Answer
Explanation: Object serialization is the process of converting an object’s state to a string from which it can later be restored.
10. The basic purpose of the toLocaleString() is to
a) return a localised object representation
b) return a parsed string
c) return a local time in the string format
d) return a localized string representation of the object
View Answer
Explanation: None.
Sanfoundry Global Education & Learning Series – Javascript Programming.
