switch case of greater than or less than variable

Question

I use this code to enter a number and compare it using less and greater than within switch case how should I do to get the correct result, only default can works

var sum=prompt("enter sum:");

// sum=50;
switch(sum)
{
case sum=0:
  alert("sucess");
  break;
case sum>50:
  alert("also sucess");
  break;
case sum<50:
  alert("failed");
default:
 alert("there is errorrrr");

}

first case should be `case sum == 0:` And 50 goes to default since none of conditions not met — ilkerkaran, Apr 12 '19 at 13:08
@Progressive Actually it's [generally considered better](https://stackoverflow.com/questions/359494/which-equals-operator-vs-should-be-used-in-javascript-comparisons) if it's `case sum === 0:` — nicholaswmin, Apr 12 '19 at 13:09
@NikKyriakides you are absolutely right. Old habits (c# guy here) die hard =) — ilkerkaran, Apr 12 '19 at 13:12

score 3 · Accepted Answer · answered Apr 12 '19 at 13:10

3

You can use switch (true):

switch (true) {
  case sum === 0:
    alert('success');
    break;
  case sum < 50:
    alert('also success');
    break;
  case sum > 50:
    alert('failed');
    break;
  default:
    alert('there is an error.')
    break;
}

Note that in your code, the first case is actually an assignment and modify sum to set it to 0.

answered Apr 12 '19 at 13:10

Étienne Miret

6,448
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1

also worth noting that the return value of a `prompt` is a string. conversion will have to happen for the comparisons to have meaningful results. – rlemon Apr 12 '19 at 13:13

Cid · Answer 2 · 2019-04-12T13:24:33.997

It actually doesn't work, as you expect, the switch statement is compared against all cases, such as :

switch (something)
{
    case 1: // something == 1 ?
    // ....
}

Actually, what you have write was interpreted such as

var sum = 42;
switch(sum)
{
    case sum < 50: // sum == sum < 50 ? -> 42 == 42 < 50 ? -> 42 == true ? false !
    // ...

Instead, you can use a switch true statement.

//        v-------     convert the prompt to a numeric value
let sum = + prompt("enter sum:");

switch(true)
{
//         VV----- notice the double equal
  case sum == 0:       // true == sum == 0 ? 
    alert("sucess");
    break;
  case sum > 50:
    alert("also sucess");
    break;
  case sum < 50:
    alert("failed");
    break;     //  <---- You forgot a break; there
  default:
    alert("there is errorrrr");
    break;
}

I'm curious to know why I've been downvoted – Cid Apr 12 '19 at 13:15 — Cid, Apr 12 '19 at 13:15

jasinth premkumar · Answer 3 · 2019-04-12T13:33:15.590

-1

ur idea works fine

sum=20;
switch(true)
{
case 50:
  alert("sucess");
  break;
case (sum>50):
  alert("also sucess");
  break;
case sum<50:
  alert("failed");
 break;        
default:
 alert("there is errorrrr");

}

edited Apr 12 '19 at 13:33

answered Apr 12 '19 at 13:11

jasinth premkumar

1,430
1
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Won't work if sum is different than 50. – Étienne Miret Apr 12 '19 at 13:12
if forgot to change variable to `true` add `break;` in 3rd case – jasinth premkumar Apr 12 '19 at 13:33

switch case of greater than or less than variable

3 Answers3