This is a Javascript algorithm to find the minimum and maximum numeric values in an array. It will ignore any members that are not numbers.

/**
* Takes an array of numbers as input and returns the highest and lowest
* value found or false if no numbers are found. Ignores any non-numeric
* members of the input array.
*
* @param values
*   An array of numbers.
* @return 
*   An array [min, max] or false if no numbers are found.
*/
function calculateRange(values) {
  
  var nums = [];
  var min = null;
  var max = null;
 
  for (var i = 0; i < values.length; i++) {  
    if (typeof values[i] == "number") {
      nums.push(values[i]);
    }
  }
 
  if (nums.length > 0) {
    min = nums[0];
    max = nums[0];
    for (var i = 0; i < nums.length; i++) {
      if (nums[i] < min) {
        min = nums[i];
      }
      if (nums[i] > max) {
        max = nums[i];
      }
    }
    return [min, max];
  }
  else {
    return false;
  } 
}

Example 1

Get the minimum and maximum values from a mixed array.

var values = [300, 2, 3, 8, 10, 3902, "banana", -1.2, "pear"];
range = calculateRange(values);
console.log(range); // Returns [ -1.2, 3902 ]

Example 2

Return false when no numbers are found.

var values = [ "banana", "pear"];
range = calculateRange(values);
console.log(range); // Returns false