JavaScript comparison

Question

Why my comparison in if doesn't work? The answer should be 8 but it returns 0.

   function findMissing(missingArray){
     var getArray = missingArray.sort();
     var myArray = [0,1,2,3,4,5,6,7,8,9]; 
       for(var i=0 ; i< myArray.length ; i++){
         for(var j=0 ; j< getArray.length ; j++){
            if(myArray[i] != getArray[j]){
                  return i;
          }
      }
   }
}
findMissing([0,3,4,5,7,2,9,1,6]);

Why do you think the answer should be 8? It clearly returns 0 when i===0 and j===1. — Ray Toal
– Ray Toal, Commented Jul 2, 2014 at 6:57

Hanky Panky · Accepted Answer · 2014-07-02 07:08:54Z

3

You can simply do it with 1 loop and array search to find the missing element. Looping over both arrays index gets changed every time and that comparison is not valid.

No Frills

 function findMissing(missingArray){
     var getArray = missingArray.sort();
     var myArray = [0,1,2,3,4,5,6,7,8,9]; 
       for(var i=0 ; i< myArray.length ; i++){
         if(getArray.indexOf(myArray[i])==-1)
            return i;
      }

  }
alert(findMissing([0,3,4,5,7,2,9,1,6]));     //8

Edit, Frills Version In fact you can create an array of all the missing elements, not just one. That be nice

 function findMissing(missingArray){
     var getArray = missingArray.sort();
     var myArray = [0,1,2,3,4,5,6,7,8,9]; 
     var returnArray=[];
       for(var i=0 ; i< myArray.length ; i++){
         if(getArray.indexOf(myArray[i])==-1)
             returnArray.push(myArray[i]);
      }
  return returnArray;
}

Fiddle

edited Jul 2, 2014 at 7:08

answered Jul 2, 2014 at 7:00

Hanky Panky

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bumbumpaw · Accepted Answer · 2014-07-02 07:00:20Z

0

  function findMissing(missingArray){
     var getArray = missingArray.sort();

     var myArray = [0,1,2,3,4,5,6,7,8,9]; 

       for(var i=0 ; i< myArray.length ; i++){

            if(myArray[i] != getArray[i]){
                  return i;          
      }
   }
}
alert(findMissing([0,3,4,5,7,2,9,1,6]));

this should work now.

answered Jul 2, 2014 at 7:00

bumbumpaw

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2 Comments

Hanky Panky Over a year ago

Nope Array size is not the same. Count those numbers

Hanky Panky Over a year ago

Although that comment is removed from the answer but still this wont answer the question. What if one array has length 10 and other has 5? you are using same index for both arrays which wont work if counts are not same.

PG1 · Accepted Answer · 2014-07-02 07:02:37Z

0

When i=0 and j=1, myArray[0]=0 and getArray=3 which are not equal, so the condition in

myArray[i] != getArray[j]

evaluates to be true and function returns i i.e. 0.

answered Jul 2, 2014 at 7:02

PG1

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