AD&D 1e magic item stats reroller (sample)

multi.js

function btw(start,val,end) {
    return val >= start && val <= end;
}

function randomInteger(val) {
    return Math.floor(Math.random()*val)+1;
}

function SwordExtraordinaryPower() {
    return "Awesome";
}

function SwordPrimaryPowerTableResult()
{
    let d100 = randomInteger(100);
    let powerResult = "";
    let nRerolls = 0;
    switch(true)
    {
        case(btw(1,d100,10)):
            powerResult = "Detect Evil";
            break;
        case(btw(11,d100,15)):
            powerResult = "Detect Gems";
            break;
        case(btw(16,d100,25)):
            powerResult = "Detect Magic";
            break;
        case(btw(26,d100,35)):
            powerResult = "Detect Metal";
            break;
        case(btw(36,d100,50)):
            powerResult = "Detect Shifting Walls and Rooms";
            break;
        case(btw(51,d100,65)):
            powerResult = "Detect Sloping Passages";
            break;
        case(btw(66,d100,75)):
            powerResult = "Find Secret Doors";
            break;
        case(btw(76,d100,85)):
            powerResult = "Find Traps";
            break;
        case(btw(86,d100,95)):
            powerResult = "See Invisible";
            break;
        case(btw(96,d100,99)):
            powerResult = SwordExtraordinaryPower();
            break;
        case(btw(100,d100,100)):
            powerResult = "Multi";
            nRerolls    = 2;
            break;
        default:
            break;
    }
    return { powerResult: powerResult, nRerolls: nRerolls }
}


function SwordPrimaryPower(aResults = [],nRerolls = 0)
{   
    let powerResult = "";
    let powerResultArray = [];
    let bDone = false;

    while (!bDone) {
        const oResult = SwordPrimaryPowerTableResult();

        if (!aResults.includes(oResult.powerResult)) {
            bDone = true;
            if (oResult.nRerolls > 0) {
                nRerolls = oResult.nRerolls;
            }
            // handle rerolls
            if (nRerolls > 0) {
                if (oResult.powerResult !== 'Multi') {
                    nRerolls--;
                }
                aResults.push(oResult.powerResult);
                return SwordPrimaryPower(aResults,nRerolls)
            }
            else {
                aResults.push(oResult.powerResult);
                if (aResults[0] == 'Multi') {
                    aResults.shift();
                }
                powerResult = aResults.join(', ');
            }
        }        
    }
    return powerResult;
}

for (let i = 0;i < 1000;i++) {
    let sPowers = SwordPrimaryPower();
    console.log('completed roll',sPowers);
}