CODEWITHSUNDEEP
javascriptarraysdigit
Griffin Obeid
Griffin Obeid

Reputation: 87

Why is the last element of my array being replaced with a 0

I have a function: 

function splitToDigits(n) {
    var digits = ("" + n).split("").map(function(item) {
        return parseInt(item, 10);
    });
    console.log(digits);
}

console.log(splitToDigits(123456784987654321));

This is returning digits = [1,2,3,4,5,6,7,8,4,9,8,7,6,5,4,3,2,0].

Any idea why the last element is 0? I noticed that when I delete 2 elements from the array it acts normally. Thanks for all the great answers! :)

Upvotes: 3

Views: 283

Answers (2)

nitobuendia
nitobuendia

Reputation: 1248

It's because Javascript is truncating numbers.

The best way to see this is by doing this console.log:

function splitToDigits(n) {
console.log(n);
var digits = ("" + n).split("").map(function(item) {
    return parseInt(item, 10);
});
}

Then, when you ran: splitToDigits(123456784987654321), you already get 123456784987654320. Hence, it has nothing to do with your code as you have still not processed it.

If you add digits, it changes to scientific notation:

splitToDigits(1234567849876543211521521251) // turns to 1.2345678498765432e+27

It's a Javascript precision issue. That's all :)

Upvotes: 1

gyre
gyre

Reputation: 16777

As Jaromanda X mentioned in the comments section above, JavaScript does not have enough precision to keep track of every digit in the integer you passed to your function.

To fix this problem, you should instead pass a string:

console.log(splitToDigits('123456784987654321'))

However, I would also like to point out that you can greatly simplify your splitToDigits method:

function splitToDigits(n) {
  return [].map.call(n + '', Number)
}

console.log(splitToDigits('123456784987654321'))
console.log(splitToDigits(1234))

Upvotes: 1

Related Questions