方法一：

function where(arr, num) {
// Find my place in this sorted array.
arr=arr.sort(function(a,b){return a-b;});
  for(var i=0;i<arr.length;i++){
    if(num>arr[i]&&num<arr[i+1]){
      return i+1;
    }  else if(num==arr[i]){
      return i;
    }  else if(i==arr.length-1){
    return i+1;
    }
  }
  return num;
}
where([40, 60], 50);

方法二：

function where(arr, num) {
  // Find my place in this sorted array.

  
  var len = arr.length,
      r = 0;
  for(var i=0;i<len;i++){
    if(num>arr[i]){
      r++;
    }
  }
  return r;
}


where([40, 60], 50);