How to Use Ranges in a Switch Case Statement Using JavaScript

Switch on ranges of integers in JavaScript

Here is another way I figured it out:

const x = this.dealer;
switch (true) {
    case (x < 5):
        alert("less than five");
        break;
    case (x < 9):
        alert("between 5 and 8");
        break;
    case (x < 12):
        alert("between 9 and 11");
        break;
    default:
        alert("none");
        break;
}

How can I use ranges in a switch case statement using JavaScript?

You have at least four options:

1. List each case

As shown by LightStyle, you can list each case explicitly:

switch(myInterval){

    case 0:
    case 1:
    case 2:
        doStuffWithFirstRange();
        break;

    case 3:
    case 4:
    case 5:
        doStuffWithSecondRange();
        break;

    case 6:
    case 7:
        doStuffWithThirdRange();
        break;

    default:
        doStuffWithAllOthers();
}

2. Use if / else if / else

If the ranges are large, that gets unwieldy, so you'd want to do ranges. Note that with if...else if...else if, you don't get to the later ones if an earlier one matches, so you only have to specify the upper bound each time. I'll include the lower bound in /*...*/ for clarity, but normally you would leave it off to avoid introducing a maintenance issue (if you include both boundaries, it's easy to change one and forget to change the other):

if (myInterval < 0) {
    // I'm guessing this is an error
}
else if (/* myInterval >= 0 && */ myInterval <= 2){
    doStuffWithFirstRange();
}
else if (/* myInterval >= 3 && */ myInterval <= 5) {
    doStuffWithSecondRange();
}
else if (/* myInterval >= 6 && */ myInterval <= 7) {
    doStuffWithThirdRange();
}
else {
    doStuffWithAllOthers();
}

3. Use case with expressions:

JavaScript is unusual in that you can use expressions in the case statement, so we can write the if...else if...else if sequence above as a switch statement:

switch (true){

    case myInterval < 0:
        // I'm guessing this is an error
        break;    
    case /* myInterval >= 0 && */ myInterval <= 2:
        doStuffWithFirstRange();
        break;

    case /* myInterval >= 3 && */ myInterval <= 5:
        doStuffWithSecondRange();
        break;

    case /* myInterval >= 6 && */ myInterval <= 7:
        doStuffWithThirdRange();
        break;

    default:
        doStuffWithAllOthers();
}

I'm not advocating that, but it is an option in JavaScript, and there are times it's useful. The case statements are checked in order against the value you give in the switch. (And again, lower bounds could be omitted in many cases because they would have matched earlier.) Even though the cases are processed in source-code order, the default can appear anywhere (not just at the end) and is only processed if either no cases matched or a case matched and fell through to the default (didn't have a break; it's rare you want to do that, but it happens).

4. Use a dispatch map

If your functions all take the same arguments (and that could be no arguments, or just the same ones), another approach is a dispatch map:

In some setup code:

var dispatcher = {
    0: doStuffWithFirstRange,
    1: doStuffWithFirstRange,
    2: doStuffWithFirstRange,

    3: doStuffWithSecondRange,
    4: doStuffWithSecondRange,
    5: doStuffWithSecondRange,

    6: doStuffWithThirdRange,
    7: doStuffWithThirdRange
};

Then instead of the switch:

(dispatcher[myInterval] || doStuffWithAllOthers)();

That works by looking up the function to call on the dispatcher map, defaulting to doStuffWithAllOthers if there's no entry for that specific myInterval value using the curiously-powerful || operator, and then calling it.

You can break that into two lines to make it a bit clearer:

var f = dispatcher[myInterval] || doStuffWithAllOthers;
f();

I've used an object for maximum flexibility. You could define dispatcher like this with your specific example:

var dispatcher = [
    /* 0-2 */
    doStuffWithFirstRange,
    doStuffWithFirstRange,
    doStuffWithFirstRange,

    /* 3-5 */
    doStuffWithSecondRange,
    doStuffWithSecondRange,
    doStuffWithSecondRange,

    /* 6-7 */
    doStuffWithThirdRange,
    doStuffWithThirdRange
];

...but if the values aren't contiguous numbers, it's much clearer to use an object instead.

Javascript -Switch Ranges on Floating Point Numbers

Don't use switch, use if/else.

if (average > 1 && average <= 1.5) {
  // do something
} else if (average > 0.5 && average <= 1) {
  // do something
} else if (average > 0 && average <= 0.5) {
  // do something
}

Switch Statement with range value

switch statements don't work like that. Your second case is checked like this: if (percent == (percent > 10 && percent < 20)) ..., which will not yield the desired result.

You could use an if / elseif / else construct:

if (percent === 0) {
  widthbytes = 0;
} else if (percent > 10 && percent < 20 {
  widthbytes = 16;
} else if (percent >= 20 && percent < 30 {
  widthbytes = 30;
} else {
  widthbytes = 0;
}

Or you could use a function that turns the ranges into constants:

function getRange(percent) {
  return Math.floor(percent/10);
}

switch(getRange(percent)) {
  case 10:
    widthbytes = 16;
    break;
  case 20:
    widthbytes = 30;
    break;
  default: 
    widthbytes = 0;  
}

Note that to get a cleaner implementation i assimilated your original case 0: into the default, since they both do the same thing. If that is not desirable, you need to change the getRange function to no longer return the same range for 0 as for any number between 0 and 10.

JavaScript switch-case statement range

It looks like you have a conditional for choosing either left or right based on size, you could break into so:

$('.list-' + ( listSize <=2 ? 'left' : 'right') ).append('<li>' + searchValue + '</li>');

Javascript Switch Range

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

jquery Using ranges in switch cases?

you could try abusing the switch fall through behaviour

var x = 5;
switch (x) {
    case  1: case 2: case 3: case 4: ...
        break;
    case 13: case 14: case 15: ...
        break;
    ...
}

which is very verbose

or you could try this

function checkRange(x, n, m) {
    if (x >= n && x <= m) { return x; }
    else { return !x; }
}

var x = 5;
switch (x) {
    case checkRange(x, 1, 12):
        //do something
        break;
    case checkRange(x, 13, 19):
    ...
}

this gets you the behaviour you would like. The reason i return !x in the else of checkRange is to prevent the problem of when you pass undefined into the switch statement. if your function returns undefined (as jdk's example does) and you pass undefined into the switch, then the first case will be executed. !x is guaranteed to not equal x under any test of equality, which is how the switch statement chooses which case to execute.

Switch or value case

There's actually a nice way to do that, notice that switch(true) will evaluate each expression.
Not always readable, but nice to know.

const money = 200;

switch (true) {
  case money < 10:
    console.log('You have $10 or less USD');
    break;
  case money < 50:
    console.log('You have $50 or less USD');
    break;
  case money < 100:
    console.log('You have $100 or less USD');
    break;
  default:
    console.log('You are rich! Over $100');
    break;
}

how to use switch case(range of number) in jquery?

You can use just as suggested here

switch (true) {
    case (tot>10 && tot<110):
        $total.html(tot);
        $risk.html('小');
        break;
    case (tot>110 && tot<310):
        $total.html(tot);
        $risk.html('大');
        break;
 }

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