Sep 23rd, 2014 at 11:36 AM

Learn JavaScript selection and loop structure with examples

Question 1.Make a JavaScript program which will take a student roll number (1 to 5) as a key and will print corresponding name (1 for “Jahid”, 2 for “Siful”, 3 for “Imran”, 4 for “Tarek”, 5 for “Shahad” ) otherwise will print “Unknown Roll” using switch-case structure. Answer:

<script>

var roll=parseInt(prompt("Enter Roll number (1-5)"));

switch(roll){
	case 1:
		document.write("Jahid");
	break;
	case 2:
		document.write("Siful");
	break;
	case 3:
		document.write("Imran");
	break;
	case 4:
		document.write("Tarek");
	break;
	case 5:
		document.write("Shahad");
	break;
	default:
		document.write("Unknown roll number");
	break;
}

</script>

Question 2. Make a JavaScript program which will take a number and only print if the number is greater than 50. Answer:

<script>
n= parseInt(prompt("Enter a number"));
If(n>50){
 document.write(n);
}
</script>

Question 3. Make a JavaScript program which will print Male if n=0 otherwise will print Female. Answer:

<script>
n= parseInt(prompt("Enter a number"));

if(n==0){
  document.write(“Male”);
}else{
  document.write(“Female”);
}
</script>

Question 4. Make a JavaScript program which will print n to m numbers according to input n, m using while, for and do-while loop. Answer: for-Loop

<script>
n= parseInt(prompt("Enter number(n)"));
m= parseInt(prompt("Enter number(m)"));
for(i=n;i<=m;i++){
  document.write(i);
}
</script>

while loop

<script>

n= parseInt(prompt("Enter number(n)"));
m= parseInt(prompt("Enter number(m)"));
i=n;
while(i<=m){
 document.write(i);
  i++;
}
</script>

do-while loop

<script>

n= parseInt(prompt("Enter number(n)"));
m= parseInt(prompt("Enter number(m)"));
i=n;
do{
  document.write(i);
  i++;
}while(i<=m);

for-in loop

<script>

var data=[3,4,56,68,65,4,4,3];

for(var i in data){
  document.write(data[i]);
}

Question 5. Make an array with five names and print the array with for-in loop. Answer:

<script>
names=[“Jahid”,”Ridon”,”Dara”,”Mukti”,”Shahad”];

for(index in names){
  document.write(names[index]);
}

</script>

Question 6. Make a JavaScript program which takes a score and will print the grade as the following criteria: a.If score is greater or equal 90 and less or equal 100 than will print A b.If score is greater or equal 80 and less or equal 89 than will print B c.If score is greater or equal 70 and less or equal 79 than will print C d.Otherwise will print F Answer:

<script>
score= parseInt(prompt("Enter your score"));
if(score>=90 && score<=100){
   document.write(“A”);
}else if(score>=80 && score<=89){
  document.write(“B”);
} else if(score>=70  && score<=79){
  document.write(“C”);
}else{
 document.write(“F”);
}
</script>