belong.js

function getIndexToIns(arr, num) {
  
  
  var sort = function(a,b) {
    return a - b;
  };
  
  var sortedArray = arr.sort(sort);
  
  var length = sortedArray.length;
  
  if(num <= sortedArray[0]) {
    return 0;
  }
  else {
    // start with the answer
    var answer = 1;
    for(answer; answer < length; answer++) {
     if( num <= sortedArray[answer]) {
       return answer;
     }
    }
    return answer;
  }
}

getIndexToIns( [10, 20, 30, 40, 50], 30 );