Palindrome Java vs JavaScript

Question

Why does this work in Java but not in JavaScript? I tried using this in Java and its working perfectly fine but I can't figure out why it's only printing "Not a palindrome" in JavaScript? thank you

 var n = 121;
 var sum = 0, r;
 var temp = n;    
 while(n>0)
   {    
    r = n % 10;   
    sum = (sum*10)+r;    
    n = n/10;    
   }    
  if(temp==sum)    
    console.log("It is a Palindrome number.");
  else  
    console.log("Not a palindrome");

It's different because java has no relationship to javascript. — NomadMaker, Dec 11 '20 at 05:20

score 4 · Accepted Answer · answered Dec 11 '20 at 03:15

You're using floating point division when you want floor division(aka integer division), since JS numbers are always floating point. To fix it, use Math.floor after the division:

var n = 121;
var sum = 0
var r;
var temp = n;    
while(n > 0){    
    r = n % 10;   
    sum = (sum * 10) + r;    
    n = Math.floor(n / 10);    
}
if(temp == sum){
    console.log("It is a palindrome number.");
}else{
    console.log("Not a palindrome");
}

score 2 · Answer 2 · answered Dec 11 '20 at 03:18

The reason this code does not same exact results in both java and javascript is because of difference in data types.

You are (most likely) declaring vars in java like:

int n = 121;    // this is strictly an integer

Whereas when you declare in javascript:

var n = 121;    // this is interpreted according to the calculation where used

So in java, n/10 will give you an integer, a round value integer answer. See this answer: https://stackoverflow.com/a/37795340/7892830

But in javascript, n/10 may give you a decimal value. Which is where your program is failing.

Solution: Use proper Math.ceil() or floor() function in javascript so it gets rounded to the nearest integer value. I'll let you figure out which one you need in this case.

Palindrome Java vs JavaScript

2 Answers2