Javascript Switch Range

Question

I recently started table top gaming and I don't want to deal with the calculations manually. Additionally, most of the apps have some kind of issue at any given time. I just began writing the basic javascript and can't seem to get the switch to work with the range. It reverts back to default. My code is below later on I will be putting the various modifiers/attributes into an array but I want the basic code to work first.

    <script>
var strMod=0;
var strength = prompt("what is your strength?");


switch(strength){
    case (strength>=0 && strength<2):
        strMod=-5;
        break;
    case (strength>=2 && strength<4):
        strMod=-4;
        break;
    case (strength>=4 && strength<6):
        strMod=-3;
        break;
    case (strength>=6 && strength<8):
        strMod=-2;
        break;
    case (strength>=8 && strength<10):
        strMod=-1;
        break;
    case (strength>=10 && strength<12):
        strMod=0;
        break;
    case (strength>=12 && strength<14):
        strMod=1;
        break;
    case (strength>=14 && strength<16):
        strMod=2;
        break;
    case (strength>=16 && strength<18):
        strMod=3;
        break;
    case (strength>=18 && strength<20):
        strMod=4;
        break;
    case (strength>=20 && strength<22):
        strMod=5;
        break;
    default:
        strMod= prompt("what is your strength modifier?");
        break;
}
console.log(strMod);
</script>

Answer 1

Change switch(strength) to switch(true). This should work since you are comparing the results of the case statements to the value true, not to the value of strength.

JSFiddle: https://jsfiddle.net/eusw15g9/

See this accepted answer for more info: Expression inside switch case statement

Answer 2

Do you really need to use switch-case? Why don't you just do something like this:

var strength = prompt("What is your strength?");
var strMod = Math.floor(strength / 2) -5;

document.getElementById("foo").innerHTML = strMod;

<div id="foo"></div>

Answer 3

A switch does not work like that -- what you pass to switch is compared via equality to all of the case values. If there is a match, the case is selected otherwise the default happens (if one is defined).

You can either switch to a long if () {} else if () {} ... else {} chain or write a function that converts the range to a numerical value and switch on that value.

The function isn't even necessary in your case:

switch(Math.ceil(strength/2)){
    case 1:
        strMod=-5;
        break;
    case 2:
        strMod=-4;
        break;
    case 3:
        strMod=-3;
        break;
    case 4:
        strMod=-2;
        break;
    ...

And then simply guard for <= 0 or >= MAX with an if before the switch.

Answer 4

A switch statement evaluates expressions using strict comparison ===. This means that the input expression will be === compare with first case clause matching in your switch. Therefore in your example above it will turn out to be default statement