JS: Switch case seemingly goes to default

November 16, 2022

I have a very simple method that receives a number and returns a text based on the range.
This is it:

getBoardLocation(num) {
    switch (num) {
        case (6 >= num >= 1):
            return 'bl';          
        case (12 >= num >= 7):
            return 'br';
        case (18 >= num >= 13):
            return 'tl'
        case (24 >= num >= 19):
            return 'tr';
        default:
            break;
    }
}

For some reason, despite being sure via breakpoints that the parameter being passed is indeed a number, and indeed in the range of one of the cases, it just goes to the default case, as seen in devtools, like here:

I feel like I missed something incredibly stupid, but I can’t figure out what.

>Solution :

there are many things wrong with your switch

try this

const isBetween = (n, start, stop) => n >= start && n <= stop 

function getBoardLocation (num) {
    switch (true) {
        case isBetween(num, 1, 6):
            return 'bl';          
        case isBetween(num, 7, 12):
            return 'br';
        case isBetween(num, 13, 18):
            return 'tl'
        case isBetween(num, 19, 24):
            return 'tr';
        default:
           throw new Error(num + 'is not valid')
    }
}
[1, 9, 14, 21].forEach(n => console.log(n, getBoardLocation(n)))

another approach could be this using some sort of a configuration object

const config = [
 {min: 1, max: 6, value: 'bl'},
 {min: 7, max: 12, value: 'br'},
 {min: 13, max: 18, value: 'tl'},
 {min: 19, max: 24, value: 'tr'}
]

 function getBoardLocation (num) {
    const res =  config.find(({min, max}) => num >= min && num <= max)?.value 
    if(!res){
      throw new Error(num + 'is not valid')
    }
    return res
 }
 
[1, 9, 14, 21].forEach(n => console.log(n, getBoardLocation(n)))