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js - is it possible to have two elements on the switch condition? [duplicate]

I'm trying to convert an if statement into a switch statement using javascript. This is the working if statement:
if(!error1(num, a_id) && !error2(num, b_id) && !error3(num, c_id) && !error4(num, d_id)) {
a.innerHTML = num;
Any tips on how to put this into a switch statement would be great. Thanks

You can make this a switch, but it's unclear why you would want to. On first glance, this isn't the kind of situation (selecting amongst a set of values and doing something different for each of them) that you use switch for.
Here's how, though I don't recommend it:
switch (false) {
case !error1(num, a_id):
case !error2(num, b_id):
case !error3(num, c_id):
case !error4(num, d_id):
// Do nothing
break;
default:
a.innerHTML = num;
break;
}
This works in JavaScript, but not in most other languages that have switch. The reason it works is that the case labels are evaluated when the execution point reaches them, and they're guaranteed to be evaluated in source code order. So you're switching on the value false, which will first be tested (using strict equality, ===) against the return value of !error1(num, a_id), and then if that doesn't match, against !error2(num, a_id), etc.; if none of them matches, then they all evaluated true, and the code in the default block runs.

Do I still need to use break after I use return in switch/case?

switch (input) {
case 1:
return "this is one";
break;
default:
break;
}
can return break the code?
Or it does what break does after return the result?

return terminates your function, so the code won't continue executing (and potentially falling through to the next case block). There's no point in using break in such a situation.

Jump case in Switch statement in (javascript) (updated )

I want to ask about switch case statement in javascript.
switch(ch){
case 0:
//do something, if condition match ,so go to case 2 and 3 (no need to go case 1)
//if not match, go to case 1, 2, and 3
break;
case 1:
//..
break;
case 2:
//..
break
case 3:
//...
}
In my code has 4 cases . There is a condition in case 0 that will skip case 1 and go to case 2. How can I do that?

The switch statement is an alternative to long if else statements (See the docs here). In your case, I believe that you should use the regular if statements.
// check if it passes case1
if (condition === case1) {
// check if it passes case1
if (condition === case2) {
// check if it passes case1
if (condition === case3) {
// do something here...
}
}
}
You may also use ternary operator, although it might be a bit hard to read as you add more conditions.

i think if else statement better suit your requirement. if you still want to do it in switch here's example :) :
var sw = function(cs){
switch(cs){
case 1:
console.log("case 1 !!!");
sw(3);
break;
case 2:
console.log("case 2 !!!");
break;
case 3:
console.log("case 3 !!!");
break;
}
};
sw(1);

I believe this's what you are looking for:
function Switcher(choice){
switch(choice){
case 1: console.log(1);;
case 4: console.log(4); break;
case 2: console.log(2); break;
case 3: console.log(3); break;
}
}
and then call Switcher(1) and see the O/P

I was looking at some logic related to switches in JavaScript today, the code I was looking at used a series of if and else statements however there were a bunch of shared logic cases which could be consolidated.
Additionally if and else statements are not exactly equal to switch statements because the runtime may implement them with jump tables making the order of execution faster than if and else.
Because you can only continue iteration patterns in ECMAScript you can hack up a solution which looks like jumping by encapsulating the logic in a fake loop like so:
(function(){
//In some function use this code
var test = 2;
Switch: while(true) switch(test){
case 2: test = 1; continue Switch;
case 1: test = 0; continue Switch;
default:alert(test);return;
};
//End code example
})();
The condition for while(true) can be changed to use another variable for state if you need to.
This gets the code as close to using jump tables as you can in other languages and a similar pattern can implement things like goto or duffs device
See also How can I use goto in Javascript?
Or Porting duff's device from C to JavaScript
Or this GIST https://gist.github.com/shibukawa/315765020c34f4543665

how to put a switch in a variable in javascript?

I'm making a little mini game and I have to put multiple switches inside of themselves, so I really need to know how to put a switch into a few words so I can make this game. I have tried it so that it's fully written out but it takes FOREVER and it is very confusing as to what is what. please help!
EDIT: im sorry i made this so confusing... let me say that again in english (: what i need to do is make it so when they either choose one of the cases or if they choose none of them (default) it would reactivate the switch. the way the person would choose is through a prompt. so what i thought i could do was make a switch into a variable then use that variable inside the switch basicly creating an endless thing that if they choose default it asks them again. here is an example i will post it in one minute
here you go!:
//this is the variable holding the switch
/*I I I I I*/
/*V V V V V*/
var switch1 = {
var choice = prompt("do you choose EXAMPLE or EXAMPLE").toUpperCase()
switch(choice) {
case 'EXAMPLE':
//this will repeat the whole prompt
switch1
break;
default:
//this will repeat it too
switch1
break; }
}
So how would i do this and make java accept this #ajaysinghdav10d?

JavaScript allows you to nest switch statements.
Have a look at this dummy example in which a service returns the location of the customer and his choice of product. Based on the combination of Choice and Location, a function to return the co-ordinates of the nearest store is called; I have used dummy values where ever necessary and alerts to explain the flow of control within the nested switch statements:
var choice = "CHO2"; /* call getChoice() function returning values from {CHO1, CHO2, ...}*/
var location = "LOC1"; /*call getLocality() function returning values from {LOC1, LOC2, ...}*/
switch (location) {
case "LOC1":
switch (choice) {
case "CHO1":
/* redirectToCHO1ofLOC1() is a function returning co-ordinates of the store*/
alert("redirectToCHO1ofLOC1");
break;
case "CHO2":
alert("redirectToCHO2ofLOC1");
break;
default:
alert("redirectToRegret");
break;
}
break;
case "LOC2":
switch (choice) {
case "CHO1":
/* redirectToCHO1ofLOC2() is a function returning co-ordinates of the store*/
alert("redirectToCHO1ofLOC2");
break;
case "CHO2":
alert("redirectToCHO1ofLOC2");
redirectToCHO2ofLOC2();
break;
default:
alert("redirectToRegret");
break;
}
break;
default:
alert("redirectToRegret");
break;
}
Updated answer based on the new context :
You must use recursion for that matter. Put your switch inside a function and call that function from the case statement of your switch, please have a look at this:
function recursiveSwitch() {
var choice = prompt("do you choose EXAMPLE or EXAMPLE").toUpperCase()
switch (choice) {
case 'EXAMPLE':
//this will repeat the whole prompt
recursiveSwitch();
break;
default:
//this will repeat it too
recursiveSwitch();
break;
}
}
Now just call the recursiveSwitch function from where ever you want and an endless loop would start.

Javascript: Multiple Switch Statements in a loop

I have a while loop and my requirement is to pass data to a variable based on first three characters of a string and another data into another variable based on last three characters of a string. So, I used two switch statements in a while loop and it looks like below
while (condition) {
switch (firstThreeChars) {
case 'a':
do this;
break;
case 'b':
do this...;
break;
}
switch (lastThreeChars) {
case 'x':
do this;
break;
case 'y':
do this...;
break;
}
}
I realized that code never reaches second switch because break in first switch-case releases control to while statement. Is there a way I can have multiple switch-case statements in a while loop? Perhaps something alternative to break statement..

That's incorrect; the break keywords terminate the switch statements, not the while. The problem here is that you're comparing your strings to single characters, so you're likely never matching any of the case statements.