Javascript Prt 2

Question 1

What's the output?
    function sum(a, b) {
      return a + b;
    }

    sum(1, "2");
    A: NaN
    B: TypeError
    C: "12"
    D: 3

Answer 1

C: “12”

Question 2

What will the following Javascript code output?
var a = [];
a[0] = 'test';
a[3] = 9;
alert( a );

Answer 2

Array: [‘test’, , , 9]

Question 3

What does the following Javascript output?
var a = 1/0;
    a. Infinity
    b. NaN
    c. Error
    d. 0

Answer 3

a. Infinity

Question 4

What does the following Javascript output (and why)?
// Self invoking function
(function () {
  var abc = "Hello";  // I will invoke myself
})();
alert( abc );

Answer 4

Error (no output)

As the abc variable is out of scope.

Question 5

Is JavaScript a subject of Java?

Answer 5

No it is not.

Question 6

Name 3 JavaScript Value Types

Answer 6

Undefined
    Null
    Booleans
    Number
    Strings
    Symbols (Objects)

Question 7

var x = 12; What value type is it in JavaScript?

Answer 7

Number.

Question 8

What does the following Javascript output?
var myvalue;
alert( myvalue );
    a. Infinity
    b. NaN
    c. Error
    d. Undefined

Answer 8

d. Undefined

undefined value possessed by unassigned variables

Question 9

what would be the output of NaN == NaN?

Answer 9

False, NaN is not equal it it self.

Question 10

In JavaScript, what does NaN stand for?

Answer 10

Not a Number.

Question 11

In JavaScript, what is the return of parseInt(“06”); ?

Answer 11

6

Question 12

What does the following Javascript output?
var a = 1/"2";
var b = a + 1;
alert( b );
    a. Infinity
    b. NaN
    c. Error
    d. None of the above

Answer 12

d. None of the above

Question 13

What does the following Javascript output?
var a = "cat" * 2
alert( a );
    a. Infinity
    b. NaN
    c. Error
    d. None of the above

Answer 13

b. NaN

Question 14

In JavaScript, what is the difference between Null and Undefined.

Answer 14

Null has no value.

Undefined is not even a value.

Question 15

In JavaScript, what is the output of “0” == false;

Answer 15

true;