OBJECTIVE TYPE QUESTIONS:
1. Fill in the blanks:
a. The while loop is repeated when the condition is true.
b. The loop that never ends is called a/an infinite
loop.
c. While loop checks the stopping
condition at the beginning of the loop.
d. The break statement is used to get out
of the loop before the entire loop gets executed.
e. The continue statements skips the
remaining code of the current iteration and transfer the control to the next
iteration of the loop.
2. Write True or False
a. There is no difference between while and do…while loops. False
b. A break statement cannot be written inside a for loop. False
c. The while loop is executed once for the false condition. False
d. A while loop may not contain a continue statement. True
e. Three statements control a for loop. True
3. Multiple choice questions:
a. How many times will the given loop will executed?
For (var I =20 ; I >= 5; I -=6)
document.write(“I=” +I)
Answer: 1
b. What will be the output of the following code?
I =10, S =1
While (I > = 5) {
S = S + I
I = I -2
}
document.write(S)
Answer: 25
c. Which one of the following is a looping statement.
Answer: for
d. Which one of the following is an infinite loop?
Answer: for (;;)
e. Which of the following loop evaluate the stopping condition at the
end of loop?
Answer: None of these
DESCRIPTIVE TYPE QUESTIONS:
1. Short answer questions
a. What is loop?
Ans: Loop is a sequence of instruction that are executed
repeatedly.
B. What are the three types of loops available
in JavaScript?
Ans: The three types of loops available in JavaScript
are:
i. for loop
ii. while loop
iii. do… while loop
c. What are the three statements comprising a for loop?
Ans: The three statements comprising a for loop are:
i. initialization
ii. condition
iii. increment/decrement
d. Name the two entry control loops?
Ans: The two entry control loop are:
i. for loop
ii. while loop
e. What happens when the condition is false
in:
i. while loop
ii. do…while loop
Ans: while loop – when the condition evaluates to false
in while loop, the statements goes outside the body of the loop and execute the
statement below.
do…while loop – when condition evaluates to
false in do…while loop, the statements come out of the loop and displays the
final value of number on the screen.
2. Long answer questions:
a. Differentiate between while, do…while, and for loops in their syntax.
Ans: i) While loop:
|
while (condition) { statements(s) } OR Initialization; while(condition
expression) { Statements(s); Increment/decrement; } |
Ans: ii. do…while loop:
|
do { Statement(s) } while (condition) OR Initialization; do { Statements(s); Increment/decrement; } While(condition
expression) |
Ans: iii. for loop:
|
for (initialization;
condition; increment/decrement) { Statement(s) } |
b. How is break statements different from continue statements? Explain
with example.
Ans: The different between break statements and continue
statements is that:
Break statements is used to get out of
the loop before the normal end of the loop. while the Continue
statements skips the remaining code of the current iteration and transfers the
control to the next iteration of the loop.
Example: of break statements
|
while(
i < 10) { If
(i==5) { break;
// breaks out of the loop completely } i = i
+1; document.write(“Counter=”
+ i + “<br/>”) } |
Here,
the loop breaks when the value reaches 5, i.e., the program exits the loop.
The break statements are used inside the while loop. The loop then jumps to
the statements after the closing brace of the loop statement. |
Example: of Continue statements
|
while(
i < 10) { If
(i==5) { continue;
// skip rest of the loop body } document.write(“Counter=”
+ i + “<br/>”) } |
Here,
the value of i reaches 5, the rest of the code is skipped and the programs
skips to the next iteration. |
c. Will a for loop execute without initialization? Explain with suitable
examples.
Ans: As we know, to execute a single statement or sets of
interactive statements repeatedly, we use looping statement which is comprises
of three statements i.e. initialization, condition, and increment/decrement.
So, for loop cannot execute without initialization.
Example:
|
for (i = 1; i <= 5;
i++) Here, the first
expression i = 1 initialize the number to a variable. It will always run
before the first execution on the loop as soon as the loop is entered. In
this case, we initialize i to 1. If this first expression i =1 is not present
in the JavaScript code then the loop will not be executed. |
d. What is infinite loop? Explain with example.
Ans: An infinite loop is a piece of code that keeps running
forever as the terminating condition is never reached.
Example:
|
while(i <=10) { document.write(“ i = ”
+i + “<br/>); i ++ } Here, if we omit the
line i ++, the loop would never end since number will never equal to 11. |
e. Can you increase/decrease the loop variable number by a value other
than 1? If yes, write the statement for the
following:
i. decrease the variable number by 1
ii. increase the variable number by 2
iii. increase the variable number by 3 iv. decrease the variable number
by 4
Ans:
i. a-=1
ii. a+=2
iii. a+=3
iv. a-=4
APLICATION BASED QUESTIONS:
1. Write the following code using for loop:
Var i = 10;
While ( i >= 1)
{
document.write(i);
i = i -
1;
}
Ans:
|
for (var i =10 ; i <=
1; i = i - 1) { Document.write(i); } |
2. Write the following code using do…while
loop:
for(var i =1 ; i <= 100; i =i + 2)
document,write(i + “<br>”);
Ans:
|
var i = 1; do { document.write(i +
“<br>”); i + i +2; } while (i <= 100) |
3. What will be the output for the following code?
var i =
1; S = 0;
while ( i <= 10)
{
S = S + i;
i = i + 2;
}
document.write(“Sum = “ + S);
Also, write how many times the loop will be
executed.
Ans: The output will be 25. The loop will run 5 times.
|
When, S will be 0 then i will
be 1 S will be 1 then i will
be 3 S will be 4 then i will
be 7 S will be 11 then i will
be 9 S will be 25 then i will
be 11 |
4. write the code mentioned in Q3 using do…while loop. What happens if
the initial value of i is 11?
Ans:
|
var i = 11; S = 0; do { document.write(“Sum =”
+S); } While (i <= 10) The loop will run one
time and will show the output as 11. Because the loop will terminate once
since the condition ( i <= 10) will be false for the initial value 11. |
5. Execute the following code to obtain the output.
var i = 1;
while ( i <= 5)
{
for ( j = 3; J <=i ; j++)
document.write( i + “<br>” + j);
}
Ans: The output will not come since it’s an infinite
loop.
Explanation:
|
Its initial value is 1
and it will satisfy first condition that is while ( i <= 5)
then it will check the condition that is ( j <= 1) which is false
since i is 1 and j is 3 ( 3 is not less
than or equal to 1), the second part is j++ which will result
to j+1 of (3 + 1 =4) and again it will check its value with i
that is (j<=i) which will again result to false. Thus the loop will
continue incrementing and checking the value (j <=i) which will
result t false all time. So, it is an infinite loop. |
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