JavaScript: Get the second digit from a number?

Solution 1:

So you want to get the second digit from the decimal writing of a number.

The simplest and most logical solution is to convert it to a string :

var digit = (''+myVar)[1];

or

var digit = myVar.toString()[1];

If you don't want to do it the easy way, or if you want a more efficient solution, you can do that :

var l = Math.pow(10, Math.floor(Math.log(myVar)/Math.log(10))-1);
var b = Math.floor(myVar/l);
var digit = b-Math.floor(b/10)*10;

Demonstration

For people interested in performances, I made a jsperf. For random numbers using the log as I do is by far the fastest solution.

Solution 2:

1st digit of number from right → number % 10 = Math.floor((number / 1) % 10)

1234 % 10; // 4
Math.floor((1234 / 1) % 10); // 4

2nd digit of number from right → Math.floor((number / 10) % 10)

Math.floor((1234 / 10) % 10); // 3

3rd digit of number from right → Math.floor((number / 100) % 10)

Math.floor((1234 / 100) % 10); // 2

nth digit of number from right → Math.floor((number / 10^n-1) % 10)

function getDigit(number, n) {
  return Math.floor((number / Math.pow(10, n - 1)) % 10);
}

number of digits in a number → Math.max(Math.floor(Math.log10(Math.abs(number))), 0) + 1 Credit to: https://stackoverflow.com/a/28203456/6917157

function getDigitCount(number) {
  return Math.max(Math.floor(Math.log10(Math.abs(number))), 0) + 1;
}

nth digit of number from left or right

function getDigit(number, n, fromLeft) {
  const location = fromLeft ? getDigitCount(number) + 1 - n : n;
  return Math.floor((number / Math.pow(10, location - 1)) % 10);
}

Solution 3:

Get rid of the trailing digits by dividing the number with 10 till the number is less than 100, in a loop. Then perform a modulo with 10 to get the second digit.

if (x > 9) {
    while (x > 99) {
        x = (x / 10) | 0;  // Use bitwise '|' operator to force integer result.
    }
    secondDigit = x % 10;
}
else {
    // Handle the cases where x has only one digit.
}