JavaScript Test Question For Elance

What is JSONP used for?

• Tracking and analyzing JSON requests
• Validating JSON requests
• Cross-domain requests
• Standardizing JSON requests

Answer: Cross-domain requests

When is a variable that a closure used generally released?

• When the variable's owning scope is released
• Never
• When it goes out of scope
• When the function closure goes out of scope

Answer: When the function closure goes out of scope

Which of the following invokes a user-defined object constructor function?

• myConstructor x = create myConstructor();
• var x = new myConstructor();
• myConstructor x = new myConstructor();
• var x = create myConstructor();

Answer: var x = new myConstructor();

Which character ends a JavaScript statement?

• An exclamation mark "!"
• A semicolon ";"
• A period "."
• A colon ":"

Answer: A semicolon ";"

Can you embed comments inside of statements? For instance: if (true /* this is a comment */) { }

• Yes
• No

Answer: Yes

Given the following, what is the value of x? var x = typeof null;

• null
• "null"
• "object"
• undefined

Answer: "object"

 Which of the following array object functions modifies the array when called?

• slice()
• concat()
• pop()
• splice()

Answer: splice()

Which of the following variable types does not exist in JavaScript?

• double
• boolean
• number
• string

Answer: double

Which is not a way to construct an array in JavaScript?

• var x = new Array(1,2,3);
• var x = array();
• var x = [];
• var x = [1,2,3];

Answer: var x = array();

Which of these is NOT a logical operator?

• &&
• &
• !
• ||

Answer: &

What is the value of thisVar in the following example? var thisVar;

• undefined
• null
• nothing
• 0

Answer: undefined

Which of the following is a correct method for creating an empty array?

• var myArray = ();
• var myArray = new Array[];
• var myArray = [];
• var myArray = array();

Answer: var myArray = [];

What is the value of the following expression? 8 % 3

• 2
• Other/Error
• 24
• 5

Answer: 2

Based on the following, what is the value of

x? var a = "A"; var x = a.concat("B");

• "B"
• ["A", " B"];
• "AB"
• "A"

Answer: "AB"

What does Math.pow(2, 3); return?

• 2 raised to the power of 3
• A random value between 2 and 3
• Variable values 2 and 3
• 6

Answer: 2 raised to the power of 3

What does the try statement do?

• It allows you test a block of code for errors.
• It asynchronously attempt to call a function.
• It attempts an HTTP request to the given URL.
• It attempts to call a function.

Answer: It allows you test a block of code for errors.

Which operator is used for string concatenation?

• &
• .
• +
• -

Answer: +

Which of the following is an Error object constructor?

• SyntaxError
• GrammarError
• EmergencyError
• StopError

Answer: SyntaxError

Which of these is a declaration in JavaScript?

• var x = 0;
• if (true) {}
• function foo() {}

Answer: var x = 0;

How do you round the number 7.25 to the nearest whole number?

• round(7.25)
• rnd(7.25)
• Math.round(7.25)
• Math.rnd(7.25)

Answer: Math.round(7.25)

Is JavaScript limited to a single file of code?

• No
• Yes
• Depends on the platform

Answer: No

Which of the following primitive values exist in JavaScript?

• linked list
• time
• tree
• boolean

Answer: boolean

Which character combination is used to create a single line comment?

• !!
• $$
• //
• --

Answer: //

Split() is a method of which constructor's prototype?

• RegExp.prototype
• String.prototype
• Array.prototype
• Number.prototype

Answer: String.prototype

How do you remove a property from an object?

• remove myObj.myProp
• delete myObj.myProp
• myObj.myProp.delete()
• myObj.properties.remove("myProp")

Answer: delete myObj.myProp

What is the difference between the following two class implementations?

 First: function Animal() { this.feed = function () { } }

Second: function Animal () { } Animal.prototype.feed = function () { };

• The second class creates a copy of the feed function for every instance; the first shares a single implementation
• They are the same
• The first class creates a copy of the feed function for every instance; the second shares a single implementation

Answer: The first class creates a copy of the feed function for every instance; the second shares a single implementation

Which character combination is used to alter the order of operations by grouping expressions?

• [ ]
• { }
• < >
• ( )

Answer: ( )

Which of the following is the syntax for an object literal (with no properties)?

• {};
• [];
• nil;
• ();

Answer: {};

JavaScript is an implementation of which language standard?

• ActionScript
• ECMAScript
• VBScript
• HTML

Answer: ECMAScript

How is an object property referenced?

• myObj<foo>
• myObj.foo
• myObj:foo
• myObj(foo)

Answer: myObj.foo

When handling an exception, which statement lets you handle the error?

• try
• catch
• finally
• throw

Answer: catch

What is the logical not operator in JavaScript?

• ~
• !
• --
• |

Answer: !

How do you find the number with the highest value of x and y?

• Math.max(x, y)
• Math.floor(x, y)
• Math.top(x, y)
• Math.ceil(x, y)

Answer: Math.max(x, y)

Which statement loops through an array?

• for (i < myArray.length; i++)
• for (i = 0; i; i <= myArray.length;)
• for (var i=0; i < myArray.length; i++)
• for (i=myArray.length; i>=0; i--)

Answer: for (var i=0; i < myArray.length; i++)

Which character ends a JavaScript statement?

• A period "."
• An exclamation mark "!"
• A colon ":"
• A semicolon ";"

Answer: A semicolon ";"

What is the following construct generally used for in JavaScript? (function () { // ... })();

• This has no effect
• To create a scope to protect code from the global scope
• To enforce strict compilation of JavaScript
• To force code to parse in a particular order

Answer: To create a scope to protect code from the global scope

How do you create an empty array using literal notation?

• var x = [Array()];
• var x = [];
• var x = [1, 2, 3];
• var x = Array();

Answer: var x = [];

Does the order of arithmetic operators matter?

• Yes
• No

Answer: Yes

What will the data look like after execution of the following code?

var data = [1, 2, 3, 4, 5, 6]; data.shift();

• [undefined, 1, 2, 3, 4, 5]
• [1, 2, 3, 4, 5]
• [6, 1, 2, 3, 4, 5]
• [2, 3, 4, 5, 6]

Answer:[2, 3, 4, 5, 6]

How do you add a new object into an array?

• myArray.add(newMember);
• myArray.push(newMember);
• myArray.pop(newMember);
• myArray.insert(newMember);

Answer: myArray.push(newMember);

Which of the following variable types does not exist in JavaScript?

• string
• double
• boolean
• number

Answer: double

What happens when the following code is executed?

function foo() { this.me = "hello"; } var x = foo(); console.log(x.me);

• "hello" is written to the console
• Runtime exception: property 'me' not found on undefined.
• Syntax error

Answer: Runtime exception: property 'me' not found on undefined.

Which of the following array object functions modifies the array when called?

• concat()
• pop()
• splice()
• slice()

Answer: splice()

Do you need to use the class pattern to be object-oriented using JavaScript?

• No
• Yes

Answer: No