Remove third input from GCD calculation if left blank

Question

I am using the following code to calculate the GCD of three numbers supplied by a user:

$('#calc').click(function(){

Math.GCD = function(numbers) {
  for (var i = 1 ; i < numbers.length ; i++){
    numbers[0] = twogcd(numbers[0], numbers[i]);
  }
  return numbers[0];

  function twogcd(first, second) {
    if (first < 0) first = -first;
    if (second < 0) second = -second;
    if (second > first) {var temp = first; first = second; second = temp;}
    while (true) {
        first %= second;
        if (first == 0) return second;
        second %= first;
        if (second == 0) return first;
    }
   }
};

Math.LCM = function(first,second) {
    return first * (second / this.GCD(first, second));
};

var first   = document.getElementById("first").value;
var second   = document.getElementById("second").value;
var third = document.getElementById("third").value;

var numbers = [first,second,third];

var GCDresult = Math.GCD(numbers);


alert(GCDresult);
});

with HTML:

<FORM NAME="calc" method="POST">

<button TYPE="button" ID="calc">CALC</button>
<input type="text" name="stuff[]" class="input-field" id="first"/>
<input type="text" name="stuff[]" class="input-field" id="second"/>
<input type="text" name="stuff[]" class="input-field" id="third"/>

</FORM>

However, I would like for this form to calculate the GCD of both 2 and 3 numbers depending on what the user inputs. Thus, if a field is left blank, the null field will be ignored and the GCD calculation will proceed with the two inputs. However, I cannot, being relatively new to JavaScript, figure out how to exclude an empty field.

Fiddle: https://jsfiddle.net/tjj7won4/40/

How might I alter the code to account for this?

Answer 1

Updated your code. Added a check for first input field isEmpty. If yes then assigned it a value of next nonEmpty input field.

updated JS :

$('#calc').click(function(){

Math.GCD = function(numbers) {
  for (var i = 1 ; i < numbers.length ; i++){
    if(numbers[0]==""){
            $.each($('.inputField'),function(){
          if($(this).val()!=""){
               numbers[0] = $(this).val();
               return false;
          }
        });
    }   
    if(numbers[0]!="" && numbers[i]!=""){
        numbers[0] = twogcd(numbers[0], numbers[i])
    }
  }
  return numbers[0];

 if (numbers[i] === '' || numbers[i] === 0) { 
    numbers[0] = twogcd(numbers[0], numbers[i])
    };
  function twogcd(first, second) {
    if (first < 0) first = -first;
    if (second < 0) second = -second;
    if (second > first) {var temp = first; first = second; second = temp;}
    while (true) {
        first %= second;
        if (first == 0) return second;
        second %= first;
        if (second == 0) return first;
    }
   }
};

Math.LCM = function(first,second) {
    return first * (second / this.GCD(first, second));
};

var first   = $("#first").val();
var second   = $("#second").val();
var third = $("#third").val();

var numbers = [first,second,third];

var GCDresult = Math.GCD(numbers);


alert(GCDresult);
});

update fiddle link