Question about js variables

Question

how to have the first number of a variable ?

Answer 1

var num = 123;
var firstDigit = num.toString().charAt(0); // not need of '+'

// however, you can use '+' for implicit string casting, but then you don't need explicit use of method .toString():

var firstDigit = (''+num).charAt(0);

// implicit string casting because concatenation with empty string (parenthesis are required to not be applied on resulted string, and not first on 'num' variable before concatenation...

// Anyway, you need to cast it again (even implicitly) to number to use it as number...
// Also, it's maybe more efficient to get it mathematically:

var n = Math.abs(num); // use a unsigned copy (to preserve the value) if you want to handle negative numbers
while (n>10) n = Math.ceil(n/10);

// ... dividing by 10 and keeping only integer part will retrieve one digit to the right of the number at each iteration, until result is between 0 and 9 included.
// Obviously, this is in case of decimal context: use the base you want instead 10 if you want to get digit in another representation than decimal ^^

Answer 2

Do you mean how to get first digit of variable stored number?
var num = 123;
var firstDigit = +num.toString().charAt(0);

Answer 3

thannks for your responces 😁😁😁👍

Answer 4

very good