Closest number in array

closest-number.js

/*
* @param num {number} - required digit
* @param arr {array} - input set of digits
* @returns {number} - closest item
*/
function closest (num, arr) {
  
  try {
    if(isNaN(num)){
      throw new Error("The 1st argument is not a number.");
    }
    if(arr.constructor !== Array){
      throw new Error("The 2nd argument is not an array of numbers.");
    }
  } catch (message) {  	
  	console.error(message);
    return null;
	}
  
  var element = arr[0];
  var difference = Math.abs(num - element);
  var len = arr.length;
  for (var i = 0; i < len; i++) {
    var newDifference = Math.abs (num - arr[i]);
    if (newDifference < difference) {
      difference = newDifference;
      element = arr[i];
    }
  }
  return element;
  
}

// Configuration.
var arr = [43,54,65,3,4,4,232,11], number = 9;

// Use timer.
console.time("t1");
for (var i=0; i<1; i++) {
	alert( closest(number, arr) );
}
console.timeEnd("t1");