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Javascript switch statement check object keys [duplicate]

These two switch statements are the same, other than the use of console.log.
When outputting the result to the chrome console I get two different results.
The first one outputs:
this is the one
while the second outputs:
1
this is the one
Why is that?
const q = 1;
switch (q) {
case '1':
answer = "one";
case 1:
answer = 1;
case 2:
answer = "this is the one";
break;
default:
answer = "not working";
}
console.log(answer);
const q1 = 1;
switch (q1) {
case '1':
console.log("one");
case 1:
console.log(1);
case 2:
console.log("this is the one");
break;
default:
console.log ("not working");
}

I put a star(*) on the lines that executed.
The switches need breaks, or else one hit can execute multiple sections.
*const q = 1;
*switch (q) {
case '1':
answer = "one";
case 1:
* answer = 1;
case 2:
* answer = "this is the one"; //changed the value of answer
* break;
default:
answer = "not working";
}
*console.log(answer); //the first line of output.
*const q1 = 1;
*switch (q1) {
case '1':
console.log("one");
case 1: //where the hit occurred.
* console.log(1); // the second line of output.
case 2:
* console.log("this is the one"); //the third line of output.
* break;
default:
console.log ("not working");
}

This is because you are not using break; at the end of each case block. Use something like this:
const q = 1;
switch (q) {
case '1':
answer = "one";
break;
case 1:
answer = 1;
break;
case 2:
answer = "this is the one";
break;
default:
answer = "not working";
}
console.log(answer);
const q1 = 1;
switch (q1) {
case '1':
console.log("one");
break;
case 1:
console.log(1);
break;
case 2:
console.log("this is the one");
break;
default:
console.log ("not working");
}
break; just means that stop the execution here and don't move to the block below, just like in your case

A switch is not like a if/else if/ else. In an if structure it only runs the code in the block that follows it.
In a switch a case statement falls through to the next. If you do not want it to fall through you add a break.
function countDown(start) {
console.log('called with: ', start);
switch (start) {
case 3:
case 'three':
console.log(3);
case 2:
case 'two':
console.log(2);
case 1:
case 'one':
console.log(1);
}
}
countDown(3); // 3 2 1
countDown('two'); // 2 1
Now when you add a break it will not fall through
function countDown(start) {
console.log('called with: ', start);
switch (start) {
case 3:
case 'three':
console.log(3);
break;
case 2:
case 'two':
console.log(2);
break;
case 1:
case 'one':
console.log(1);
break;
}
}
countDown(3); // 3
countDown('two'); // 2

If we execute each line of code or verify each line code, you can see, in first switch case is executed case 1 and thencase 2, which makes value = this is the one now the break is executed and we are out of switch case 1.
Now,console.log(answer); hits and prints this is the one
Next, q1 =1
case 1:
console.log(1);
case 2:
console.log("this is the one");
Both of the above statement executes since, case 1 is correct match for switch case number 2, but there is no break so case 2 is also executed.
Hence, you see this output.
You can also refer these links also: Why is Break needed when using Switch?
https://javascript.info/switch

You need to add break to skip the next switch case.
switch (month) {
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
conosle.log('case is 1 to 12');
break;
case 13:
console.log('case 13');
break;

const q = 1;
switch (q) {
case '1':
answer = "one";
case 1:
answer = 1;
case 2:
answer = "this is the one";
break;
default:
answer = "not working";
}
console.log(answer);
switch case default behaviour is that when a case will get true value then the following case statements will run without checking the condition . in this case case 1 is implemented as true so the next cases will not evaluate .
const q1 = 1;
switch (q1) {
case '1':
console.log("one");
case 1:
console.log(1);
case 2:
console.log("this is the one");
break;
default:
console.log ("not working");
}
in your second code , case 1 will evaluated as true so the compiler will not evaluate your case 2 . it will directly go to the case 2 block and console that until compiler find a break s

Is it possible to do something on all switch cases by default without repeating?

Is there a way to repeat a sentence inside of a switch for every case but for default? Without repeating the action inside every case, of course.
I have this:
this.set_estate = function(state){
switch(state){
case 'LOADING':
current= est[state];
break;
case 'WRITING':
current= est[state];
//statements_2
break;
case 'WAITING':
current= est[state];
//statements_3
break;
default:
console.log('tried to set state: '+state);
break;
}
}
And I'd like to know if it could be shifted into something similar to:
this.set_estate = function(state){
switch(state){
case 'LOADING':
case 'WRITING':
case 'WAITING':
current= est[state];
continue;
case 'LOADING':
//statements_1
break;
case 'WRITING':
//statements_2
break;
case 'ESPERANDO':
//statements_3
break;
default:
console.log('tried to set state: '+state);
break;
}
}

Write another switch statement before this to do just the common lines. This would prevent you from writing the code multiple times, if that is your concern.

Switch with random not working

This is my current jScript code:
(modified STILL doesn't work)
function changeBG(){
document.getElementById('imgbox').src = switch(eval(rand())){
case 1: "img/img3.jpg";
break;
case 2: "img/img2.jpg";
break;
case 3: "img/img3.jpg";
break;
case 4: "img/img4.jpg";
break;
case 5: "img/img5.jpg";
break;
default: "img/background.jpg";
break;
}
}
function rand(){
return (Math.ceil((Math.random()*10)/2));
}
my HTML:
<input id="BGchange" type="button" onclick="changeBG()" value=">"/>
If I do something like this:
document.getElementById('imgbox').src = "img/img1.jpg";
It just works: I click on my button, the image changes, no problem. Fact is I want the image to change to a random one between 5 each time the button is clicked; to do this I wanted to use a switch that works with a random choice inside it.
What is wrong with my coding?! :( (I cant use jQuery or anything, just pure javascript, html and css, thats what the professor said at least)
Thank you <3

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/switch
The switch-statement "executes" your Strings ("img/imgX.jpg") instead of returning them, so you may want put the switch in a function and then do
case 1: return "img/img3.jpg";
...
and keep in mind that each case of a switch statement must be terminated with break, otherwise the following case-Blocks will be executed as well!

Your function return an integer, while your switch case is looking for a string.
Remove quotes from the switch cases and everything should work.
function changeBG(){
document.getElementById('imgbox').src = switch(rand()){
case 1: "img/img3.jpg";
break;
case 2: "img/img2.jpg";
break;
case 3: "img/img3.jpg";
break;
case 4: "img/img4.jpg";
break;
case 5: "img/img5.jpg";
break;
default: "img/background.jpg";
}
}

Switch statement for multiple cases in JavaScript

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;
}

JavaScript comma separation not working with switch case

In case of comma separation not working with swtich case. is there any way to do this?
switch(test)
{
case 0,1://not working it take last one (1)
"test"
break;
case 2,3://not working it take last one (3)
"test2"
break;
case 4,5://not working it take last one (5)
"test3"
break;
}
How can i add further number with each case?

switch(test)
{
case 0: case 1:
"test"
break;
case 2: case 3:
"test2"
break;
case 4: case 5:
"test3"
break;
}

You should fall through (which is considered a bad practice)
switch(test)
{
case 0:
case 1://not working it take last one (1)
"test"
break;
case 2:
case 3://not working it take last one (3)
"test2"
break;
}