//This is my Problem
Complete the getLetter(s) function in the editor. It has one parameter: a string, , consisting of lowercase English alphabetic letters (i.e., a through z). It must return A, B, C, or D depending on the following criteria:
If the first character in string is in the set {aeiou}, then return A.
If the first character in string is in the set {bcdfg}, then return B.
If the first character in string is in the set {hjklm},, then return C.
If the first character in string is in the set {npqrstvwxyz}, then return D.
I am trying to implement the above scenarion and to dthis I have written the following code.
//Here is my code
function getLetter(s) {
let letter;
// Write your code here
switch (s) {
case s.match(/[aeiou]/g).includes(s[0]):
letter = 'A'
break;
case s.match(/[bcdfg]/g).includes(s[0]):
letter = 'B'
break;
case s.match(/[hjklm]/g).includes(s[0]):
letter = 'C';
break;
case s.match(/[npqrstvwxyz]/g).includes(s[0]):
letter = 'D';
break;
default:
console.log("hello")
}
return letter
}
The code is showing error. Would any help me to figure it out? How can I implement the above task using switch statement.
I don't know that much switch case, but maybe you can use parenthesis for the switch statement and if "s.match(/[aeiou]/g).includes(s[0])" return true or false
And you forgot ";" after the two first assignment
the way you wrote the switch case may be partially correct in GoLang. but in Javascript, it is not possible to achieve this using Switch-Case statement.
Better try using if-else-if statement something like below
if(s.test(/^[aeiou]/)) {
return 'A';
} else if(s.test(/^[bcdfg]/)) {
return 'B'
}
Check out this: Switch statement for string matching in JavaScript. The issue is that match returns null, which breaks the switch statement.
Use
switch(s){
case str.match(/^xyz/)?.input:
//code
break;
This stops the match from returning null.
Based on how you're using this, you actually want to switch (true) and not switch (s)
i.e. when you have a case y in a switch (x), the test being done is x === y; so you want to do true === some.test()
const s = 'a';
switch (true) {
case /a/.test(s):
console.log('first match');
break;
case /b/.test(s):
console.log('second match');
break;
default:
console.log('no match');
break;
}
Will log first match because
/a/.test('a') is true
and true /* from switch */ === true /* from case test */
Note that in most cases switch can also be written as if..else if..else.
Base your decision on which to use by which is the most readable (err on the side of if patterns)
The above example written as an if might look like this
const s = 'a';
if (/a/.test(s)) {
console.log('first match');
} else if (/b/.test(s)) {
console.log('second match');
} else {
console.log('no match');
}
New to JavaScript so please forgive me if this has an obvious answer. I'm trying to get a switch statement to output a specific phrase depending on the value of an input box, however it will only output the default option. What have I done wrong? Thanks.
<input id="inputIQ" type="number"/>
<button onclick="inputIQFunction()">Submit</button>
<script>
function inputIQFunction()
{
var userinput = document.getElementById("inputIQ").value;
switch (userinput) {
case userinput <= 10:
alert("Less than 10");
break;
case userinput > 10:
alert("Greater than 10");
break;
default:
alert("Please input value");
break;
}
}
</script>
Basically, switch doesn't support conditional expressions. It just jumps to the value according to the cases.
If you put true in the switch (true) part, it'll jump to the case whose have true value.
Try like this
switch (true) {
case userinput <= 10:
alert("Less than 10");
break;
case userinput > 10:
alert("Greater than 10");
break;
default:
alert("Please input value");
break;
}
You cannot use logical conditions in your switch statement. It actually compares your userinput to a result of condition (true \ false), which never occurs.
Use conditions instead:
function inputIQFunction() {
function getIQFunctionOutput(inputValue) {
var parsedInput = parseInt(inputValue);
if (Number.isNaN(parsedInput))
return "Please, enter a correct value";
return parsedInput <= 10
? "Less or equal than 10"
: "Greater than 10";
}
var userinput = document.getElementById("inputIQ").value;
var output = getIQFunctionOutput(userinput);
alert(output);
}
<input id="inputIQ" type="number" />
<button onclick="inputIQFunction()">Submit</button>
P.S. You can actually use switch with logical statements this way:
switch (true) {
case userinput <= 10:
break;
case userinput > 10:
break;
}
but I would highly recommend not to use this approach because it makes your code harder to read and maintain.
Try like this:
<input id="inputIQ" type="number"/>
<button onclick="inputIQFunction()">Submit</button>
<script>
function inputIQFunction() {
var userinput = document.getElementById("inputIQ").value;
userinput = parseInt(userinput);
switch (true) {
case userinput <= 10:
alert("Less than 10");
break;
case userinput > 10:
alert("Greater than 10");
break;
default:
alert("Please input value");
break;
}
}
</script>
A switch works by testing the value of the expression in switch(expression) against the values of each case until it finds one that matches.
In your code, the userinput in switch(userInput) is a string, but your two case statements both have a value of either true or false. So you want to use switch(true) - that's how you get a switch to work with arbitrary conditions for each case. In context:
switch(true) {
case userinput <= 10:
alert("Less than 10");
break;
case userinput > 10:
alert("Greater than 10");
break;
default:
alert("Please input value");
break;
}
I know this is an old thread but I'm just starting out on JS (one week in) and this is the simplest thing I could create just so the logic is understood.
Switch appears to work only by true/false when using a user input value.
My script looks like:
<script>
document.getElementById("click").onclick = function () {
var day = document.getElementById("day").value;
switch (true) {
case day == 1:
document.write("Monday");
break;
case day == 2:
document.write("Tuesday");
break;
default:
document.write("Please enter valid number")
}
</script>
Like I said I'm only a week into this but I'm making a small portfolio for myself with these little things that courses may not teach, I'm open to any one wishing to offer me help learning also, hope it helps with understanding the logic.
You are not fulfilling the requirements of 'switch & case'
userinput <= 10:
It means 'true'
because '<=' is a comparison operator. It compares 'userinput' and ’10'(given value) and give you an answer in boolean(i.e. true or false).
But, here in switch case you need an integer value.
Another
You have entered this
'switch (userinput)' here 'switch' considering 'userinput' a string that should be integer,
You can fix it with this.
switch (eval(userinput))
I need multiple cases in switch statement in JavaScript, Something like:
switch (varName)
{
case "afshin", "saeed", "larry":
alert('Hey');
break;
default:
alert('Default case');
break;
}
How can I do that? If there's no way to do something like that in JavaScript, I want to know an alternative solution that also follows the DRY concept.
Use the fall-through feature of the switch statement. A matched case will run until a break (or the end of the switch statement) is found, so you could write it like:
switch (varName)
{
case "afshin":
case "saeed":
case "larry":
alert('Hey');
break;
default:
alert('Default case');
}
This works in regular JavaScript:
function theTest(val) {
var answer = "";
switch( val ) {
case 1: case 2: case 3:
answer = "Low";
break;
case 4: case 5: case 6:
answer = "Mid";
break;
case 7: case 8: case 9:
answer = "High";
break;
default:
answer = "Massive or Tiny?";
}
return answer;
}
theTest(9);
Here's different approach avoiding the switch statement altogether:
var cases = {
afshin: function() { alert('hey'); },
_default: function() { alert('default'); }
};
cases.larry = cases.saeed = cases.afshin;
cases[ varName ] ? cases[ varName ]() : cases._default();
In Javascript to assign multiple cases in a switch, we have to define different case without break inbetween like given below:
<script>
function checkHere(varName){
switch (varName)
{
case "saeed":
case "larry":
case "afshin":
alert('Hey');
break;
case "ss":
alert('ss');
break;
default:
alert('Default case');
break;
}
}
</script>
Please see example click on link
I like this for clarity and a DRY syntax.
varName = "larry";
switch (true)
{
case ["afshin", "saeed", "larry"].includes(varName) :
alert('Hey');
break;
default:
alert('Default case');
}
If you're using ES6, you can do this:
if (['afshin', 'saeed', 'larry'].includes(varName)) {
alert('Hey');
} else {
alert('Default case');
}
Or for earlier versions of JavaScript, you can do this:
if (['afshin', 'saeed', 'larry'].indexOf(varName) !== -1) {
alert('Hey');
} else {
alert('Default case');
}
Note that includes won't work in some browser including older IE versions, but you could patch things up fairly easily. See the question determine if string is in list in javascript for more information.
My situation was something akin to:
switch (text) {
case SOME_CONSTANT || ANOTHER_CONSTANT:
console.log('Case 1 entered');
break;
case THIRD_CONSTANT || FINAL_CONSTANT:
console.log('Case 2 entered');
break;
default:
console.log('Default entered');
}
The default case always entered. If you're running into a similar multi-case switch statement issue, you're looking for this:
switch (text) {
case SOME_CONSTANT:
case ANOTHER_CONSTANT:
console.log('Case 1 entered');
break;
case THIRD_CONSTANT:
case FINAL_CONSTANT:
console.log('Case 2 entered');
break;
default:
console.log('Default entered');
}
Adding and clarifying Stefano's answer, you can use expressions to dynamically set the values for the conditions in switch, e.g.:
var i = 3
switch (i) {
case ((i>=0 && i<=5) ? i : -1):
console.log('0-5');
break;
case 6: console.log('6');
}
So in your problem, you could do something like:
var varName = "afshin"
switch (varName) {
case (["afshin", "saeed", "larry"].indexOf(varName)+1 && varName):
console.log("hey");
break;
default:
console.log('Default case');
}
Although it is so much DRY...
In Node.js it appears that you are allowed to do this:
data = "10";
switch(data){
case "1": case "2": case "3": // Put multiple cases on the same
// line to save vertical space.
console.log("small");
break;
case "10": case "11": case "12":
console.log("large");
break;
default:
console.log("strange");
break;
}
This makes for much more compact code in some cases.
I use it like this:
switch (true){
case /Pressure/.test(sensor):
{
console.log('Its pressure!');
break;
}
case /Temperature/.test(sensor):
{
console.log('Its temperature!');
break;
}
}
Some interesting methods. For me the best way to solve is using .find.
You can give an indication of what the multiple cases are by using a suitable name inside your find function.
switch (varName)
{
case ["afshin", "saeed", "larry"].find(firstName => firstName === varName):
alert('Hey');
break;
default:
alert('Default case');
break;
}
Other answers are more suitable for the given example but if you have multiple cases to me this is the best way.
It depends. Switch evaluates once and only once. Upon a match, all subsequent case statements until 'break' fire no matter what the case says.
var onlyMen = true;
var onlyWomen = false;
var onlyAdults = false;
(function(){
switch (true){
case onlyMen:
console.log ('onlymen');
case onlyWomen:
console.log ('onlyWomen');
case onlyAdults:
console.log ('onlyAdults');
break;
default:
console.log('default');
}
})(); // returns onlymen onlywomen onlyadults
<script src="https://getfirebug.com/firebug-lite-debug.js"></script>
You can use the 'in' operator...
It relies on the object/hash invocation, so it's as fast as JavaScript can be.
// Assuming you have defined functions f(), g(a) and h(a,b)
// somewhere in your code,
// you can define them inside the object, but...
// the code becomes hard to read. I prefer it this way.
o = { f1:f, f2:g, f3:h };
// If you use "STATIC" code can do:
o['f3']( p1, p2 )
// If your code is someway "DYNAMIC", to prevent false invocations
// m brings the function/method to be invoked (f1, f2, f3)
// and you can rely on arguments[] to solve any parameter problems.
if ( m in o ) o[m]()
You can do this:
alert([
"afshin",
"saeed",
"larry",
"sasha",
"boby",
"jhon",
"anna",
// ...
].includes(varName)? 'Hey' : 'Default case')
or just a single line of code:
alert(["afshin", "saeed", "larry",...].includes(varName)? 'Hey' : 'Default case')
a little improvement from ErikE's answer
I can see there are lots of good answers here, but what happens if we need to check more than 10 cases? Here is my own approach:
function isAccessible(varName){
let accessDenied = ['Liam', 'Noah', 'William', 'James', 'Logan', 'Benjamin',
'Mason', 'Elijah', 'Oliver', 'Jacob', 'Daniel', 'Lucas'];
switch (varName) {
case (accessDenied.includes(varName) ? varName : null):
return 'Access Denied!';
default:
return 'Access Allowed.';
}
}
console.log(isAccessible('Liam'));
The problem with the above approaches, is that you have to repeat the several cases every time you call the function which has the switch. A more robust solution is to have a map or a dictionary.
Here is an example:
// The Map, divided by concepts
var dictionary = {
timePeriod: {
'month': [1, 'monthly', 'mensal', 'mês'],
'twoMonths': [2, 'two months', '2 months', 'bimestral', 'bimestre'],
'trimester': [3, 'trimesterly', 'quarterly', 'trimestral'],
'semester': [4, 'semesterly', 'semestral', 'halfyearly'],
'year': [5, 'yearly', 'annual', 'ano']
},
distance: {
'km': [1, 'kms', 'kilometre', 'kilometers', 'kilometres'],
'mile': [2, 'mi', 'miles'],
'nordicMile': [3, 'Nordic mile', 'mil (10 km)', 'Scandinavian mile']
},
fuelAmount: {
'ltr': [1, 'l', 'litre', 'Litre', 'liter', 'Liter'],
'gal (imp)': [2, 'imp gallon', 'imperial gal', 'gal (UK)'],
'gal (US)': [3, 'US gallon', 'US gal'],
'kWh': [4, 'KWH']
}
};
// This function maps every input to a certain defined value
function mapUnit (concept, value) {
for (var key in dictionary[concept]) {
if (key === value ||
dictionary[concept][key].indexOf(value) !== -1) {
return key
}
}
throw Error('Uknown "'+value+'" for "'+concept+'"')
}
// You would use it simply like this
mapUnit("fuelAmount", "ltr") // => ltr
mapUnit("fuelAmount", "US gal") // => gal (US)
mapUnit("fuelAmount", 3) // => gal (US)
mapUnit("distance", "kilometre") // => km
// Now you can use the switch statement safely without the need
// to repeat the combinations every time you call the switch
var foo = 'monthly'
switch (mapUnit ('timePeriod', foo)) {
case 'month':
console.log('month')
break
case 'twoMonths':
console.log('twoMonths')
break
case 'trimester':
console.log('trimester')
break
case 'semester':
console.log('semester')
break
case 'year':
console.log('year')
break
default:
throw Error('error')
}
One of the possible solutions is:
const names = {
afshin: 'afshin',
saeed: 'saeed',
larry: 'larry'
};
switch (varName) {
case names[varName]: {
alert('Hey');
break;
}
default: {
alert('Default case');
break;
}
}
If your case conditions are complex, many case value matches, or dynamic value match required, then it may be best to move that case matching logic to handler child functions.
In your case, if say you had thousands of usernames to match against for a security permissions check for example, this method is cleaner option, more extensible, exposing the high level multi-way branch logic without getting swamped in a long list of case statements.
switch (varName)
{
case checkPatternAdministrator(varName):
alert('Hey');
break;
case checkPatternUserTypeA(varName):
alert('Hey2');
break;
case checkPatternUserTypeB(varName):
alert('Hey3');
break;
default:
alert('Default case');
break;
}
function checkPatternAdministrator(varName) {
// Logic to check Names against list, account permissions etc.
// return the varName if a match is found, or blank string if not
var matchedAdministratorName = varName;
return matchedAdministratorName;
}
Here is one more easy-to-use switch case statement. which can fulfill your requirement. We can use the find method in the switch statement to get the desire output.
switch(varname){
case["afshin","saeed","larry"].find(name => name === varname):
alert("Hey")
break;
default:
alert('Default case');
break;
}
The switch statement is used to select one of many code blocks to execute based on a condition
the value in the switch expression is compared to the different values provided
if there is a match the code block related to it will be executed
if there is no match the default block is executed
syntax:
switch(expression) {
case x:
// code block
break;
case y:
// code block
break;
default:
// code block
}
NOTE:
It must be noted that if the break statement is omitted then the next block will be executed as well even if they does not match with switch expression. So don't forget to add the break statement at the end of each code block if you don't want to get the specified behaviour
A practical example:
the following code returns the current day of the week in strings based on an integer (provided by 'new Date().getDay()')
switch (new Date().getDay()) {
case 0:
day = "Sunday";
break;
case 1:
day = "Monday";
break;
case 2:
day = "Tuesday";
break;
case 3:
day = "Wednesday";
break;
case 4:
day = "Thursday";
break;
case 5:
day = "Friday";
break;
case 6:
day = "Saturday";
}
the code samples were taken from W3Schools
Another way of doing multiple cases in a switch statement, when inside a function:
function name(varName){
switch (varName) {
case 'afshin':
case 'saeed':
case 'larry':
return 'Hey';
default:
return 'Default case';
}
}
console.log(name('afshin')); // Hey
Cleaner way to handle that
if (["triangle", "circle", "rectangle"].indexOf(base.type) > -1)
{
//Do something
}else if (["areaMap", "irregular", "oval"].indexOf(base.type) > -1)
{
//Do another thing
}
You can do that for multiple values with the same result
Just change the switch condition approach:
switch (true) {
case (function(){ return true; })():
alert('true');
break;
case (function(){ return false; })():
alert('false');
break;
default:
alert('default');
}
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Example1</title>
<link rel="stylesheet" href="css/style.css" >
<script src="js/jquery-1.11.3.min.js" type="text/javascript"></script>
<script>
function display_case(){
var num = document.getElementById('number').value;
switch(num){
case (num = "1"):
document.getElementById("result").innerHTML = "You select day Sunday";
break;
case (num = "2"):
document.getElementById("result").innerHTML = "You select day Monday";
break;
case (num = "3"):
document.getElementById("result").innerHTML = "You select day Tuesday";
break;
case (num = "4"):
document.getElementById("result").innerHTML = "You select day Wednesday";
break;
case (num = "5"):
document.getElementById("result").innerHTML = "You select day Thusday";
break;
case (num = "6"):
document.getElementById("result").innerHTML = "You select day Friday";
break;
case (num = "7"):
document.getElementById("result").innerHTML = "You select day Saturday";
break;
default:
document.getElementById("result").innerHTML = "You select day Invalid Weekday";
break
}
}
</script>
</head>
<body>
<center>
<div id="error"></div>
<center>
<h2> Switch Case Example </h2>
<p>Enter a Number Between 1 to 7</p>
<input type="text" id="number" />
<button onclick="display_case();">Check</button><br />
<div id="result"><b></b></div>
</center>
</center>
</body>
You could write it like this:
switch (varName)
{
case "afshin":
case "saeed":
case "larry":
alert('Hey');
break;
default:
alert('Default case');
break;
}
For me this is the simplest way:
switch (["afshin","saeed","larry"].includes(varName) ? 1 : 2) {
case 1:
alert('Hey');
break;
default:
alert('Default case');
break;
}