//shuffle array of 10 integers to get a random value
var rand_10 = [0,1,2,3,4,5,6,7,8,9];
fisherYates(rand_10);

//Set weightedProb
weightedProb[0] = probType[0];
weightedProb[1] = probType[0];
weightedProb[2] = probType[0];
.
.
.
weightedProb[8] = probType[0];
weightedProb[9] = probType[1];

theProblem = weightedProb[rand_10[0]];
if(rand_10[0] == 0 || rand_10[0] == 1 || rand_10[0] == 2 || rand_10[0] == 3 ||rand_10[0] == 4||rand_10[0] == 5||rand_10[0] == 6||rand_10[0] == 7||rand_10[0] == 8){
  //do something
}else if(rand_10[0] ==9){
  //do something else
}

if(rand_10[0] >= 0 && rand_10[0] <= 8){
  //do something
}else if(rand_10[0] == 9){
  //do something else
}

if ([0,1,2,3,4,5,6,7,8].indexOf(rand_10[0]) > -1) {
}

if(rand_10[0] >= 0 && rand_10[0] <= 8){
  //do something
}else if(rand_10[0] ==9){
  //do something else
}

if (rand_10[0] in arr) {
//...
}

switch(rand_10[0]) {
   case 0:
   case 1:
   case 2:
   case 3:
   case 4:
   case 5:
   case 6:
   case 7:
   case 8:
     // do something
     break;
   case 9:
     // do something
     break;
 }

function weightedRandomIndex(weights) {
    var sum = 0, i, x, n=weights.length, rnd;
    for (i=0; i<n; i++) {
        sum += weights[i];
    }
    rnd = Math.floor(Math.random()*sum);
    for (i=0, x=0; i<n; i++) {
        x += weights[i];
        if (x > rnd) return i;
    }
}

var idx = weightedRandomIndex([9,1]);  // 9 to 1 chance for index 0 over index 1