L11, Switch, break and continue statements, CSE 202, BN11.pdf

Course Code: CSE 202
Course Title: Computer Programming Lab
Lecture 11: Switch, break and continue
statements
Course Teacher: Saurav Barua (SB)
Assistant Professor, Dept. of CE, DIU
Phone: +88-01715334075
Email: saurav.ce@diu.edu.bd

Contents
2
Alternatives
between switch
and if-else
Continue
statement
Break
statement
Comparison
continue and
break
Switch
statement
.
Alternatives among
for, while and do-
while loops

switch statement
3
 The switch statement is used to perform different actions based
on different conditions.
This is how it works:
 The switch expression is evaluated once.
 The value of the expression is compared with the values of
each case.
 If there is a match, the associated block of code is executed.
 If there is no match, the default code block is executed.

switch statement
4
Syntax:
switch(expression) {
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}

continue statement
5
 The continue statement "jumps over" one iteration in the loop.
Syntax:
continue;

break statement
6
 The break statement "jumps out" of a loop.
Syntax:
break;

Comparison between continue and break statement
7
Program with continue statement
 Program to count 1 to 5, discontinue
at 4 and display in the console.
Program with break statement
 Program to count 1 to 5, skip 4 and
display in the console.
for(i=1; i<6; i++){
if(i== 4)
continue;
console.log(i);
}
/*Output:
1
2
3
5
*/
for(i=1; i<6; i++){
if(i== 4)
break;
console.log(i);
}
/*Output:
1
2
3
*/

If-else / switch alternatives
8
let score = 65;
function result(){
if(score>=90)
grade = "A";
else if(score>=80 && score<90)
grade = "B";
else if(score>=70 && score<80)
grade = "C";
else
grade = "F";
return grade;
}
outputResult = result();
console.log(outputResult);
Program with if- else if- else statement
 Program to calculate grade of a student from his
test score and display in the console.
Program with switch statement
let score = 73;
function result(){
switch(true){
case score>=90:
grade = "A";
break;
case score>=80:
grade = "B";
break;
case score>=70:
grade = "C";
break;
default:
grade = "F";
}
return grade;
}
outputResult = result();
console.log(outputResult);

for / while/ do-while alternatives
9
Program for loop
 Program to count 5 to 1 numbers and display in the console.
Program with while loop Program with do-while loop
for(let i = 5; i>0; i--){
console.log(i);
}
let i = 5;
while(i>0){
console.log(i);
i--
}
let i = 5;
do{
console.log(i)
i--;
}while(i>0);

Use of continue statement
10
Case study: The SPT N-value is the number of blows required to drive a drill rod
and soil sampler 12 inches into the ground during a standard penetration test
(SPT). The N-value is the sum of the number of blows required for the second and
third 6-inch intervals.
Example problem:
Program to calculate N-value of a SPT soil test where number of blows = [12, 18,
21] and display result in the browser.
const blows = [12, 18, 21];
let nVal = 0;
for (let i = 0; i<blows.length; i++){
if(blows[i] == blows[0])
continue;
else
nVal += blows[i];
}
console.log(nVal)
// output: 39

Worked out example
11
Example 11: Program to classify data based on specified range using switch
statement. (Classify water sample based on degree of hardness (mg/l as CaCO3)
and display result in the browser using switch, where <50 is soft, 50-150 is
moderately hard, 150-300 is hard and >300 is very hard.)
Google drive link:
https://drive.google.com/drive/folders/1DNqm-
2rFkuRJXg5Cb6PMa9fgd82mE-pD?usp=drive_link
Git-hub link:
https://github.com/sauravbarua02/waterHardnessSwitch

html codes
13
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, initial-
scale=1.0">
<title>Hardness of Water</title>
<link rel="stylesheet" href="style.css">
</head>
<body>
<div class="container" id="container">
</div>
<script src="app.js"></script>
</body>
</html>

css codes
14
body{
margin: 0;
padding: 0;
height: 100%;
background: url("images.jpg");
background-repeat: no repeat;
background-size: cover;
background-attachment: fixed;
background-position: center;
}
.container{
background-color: rgba(148, 60, 60, 0.1);
display: flex;
justify-content: center;
align-items: center;
height: 350px;
width: 350px;
margin: 30px auto;
padding: 20px;
border-radius: 10px;
border: 1px solid rgba(255, 255,255, 0.3);
box-shadow: 3px 3px 3px rgba(0,0,0,0.1);
font-size: larger;
backdrop-filter: blur(5px);
}

JS codes
15
const containerEl =
document.getElementById("container");
let hardnessValue = 160;
function check(){
switch(true){
case hardnessValue>=300:
result = "Very hard water";
break;
result = "Hard water";
break;
result = "Moderately hard water";
break;
case hardnessValue<50:
result = "Soft water";
break;
default:
result = "Not a number";
}
return result;
}
function display(){
let output = check();
containerEl.innerText = "The sample is
"+output;
}
display();

Class tasks
16
Task 11.1: Program to classify soil sample based on plasticity index (%) and display result in
the browser using switch, where 0 is non-plastic, <7 is low-plastic, 7-17 is medium-plastic and
>17 is highly-plastic.
Task 11.2: Program to classify aggregate sample based on aggregate impact value (%) and
display result in the browser using switch, where <10% is exceptionally strong, 10-20% is
strong, plastic, 20-30% is acceptable for road surfaces and >30% is weak for road surfaces.
Task 11.3: Program to classify column design based on D/C ratio obtained from ETABS analysis
and display result in the browser using switch, where <0.7 is not cost effective design, 0.7-1.0
is ideal design and >1.0 is not safe design.
Task 11.4: Program to classify open channel flow based on Raynold’s number and display
result in the browser using switch, where <2000 is laminar flow, 2000-4000 is unsteady flow
and >4000 is turbulent flow.
Task 11.5: Program to classify fresh natural water sample based on TDS (mg/l) and display
result in the browser using switch, where <20 is low, 20-120 is average and 120-1000 is high

L11, Switch, break and continue statements, CSE 202, BN11.pdf

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