How to check if a number that starts with a letter

Question

I have a code below that matches a remainder of an 8 digit number to a letter when divided by 23.

function dniLetter( dni ) {

var lockup = 'TRWAGMYFPDXBNJZSQVHLCKE'
var result = ''; 
var remainder = dni % 23;
result = lockup.charAt(remainder)

return result; }

How could I improve if the number starts with a negative number (like -2) or start with a letter (A1234567)?

What do you want to **do** if it is a negative number or if it comes with a letter? — Buzinas, Oct 07 '15 at 20:56
`function isLetter(str) { return str.length === 1 && str.match(/[a-z]/i); }` — Emilio Gort, Oct 07 '15 at 20:57

score 1 · Answer 1 · answered Oct 07 '15 at 21:09

1

For the negative numbers, you should try replacing dni % 23 by ((dni % 23) + 23) % 23. It will do exactly what you want.

answered Oct 07 '15 at 21:09

Benjamin Amelot

103
1
8

score 0 · Answer 2 · answered Oct 07 '15 at 20:56

0

You should use regular expressions.

/^[a-zA-Z-]/.test(yourString) returns true on the specified conditions (and even if it starts with '-A' for instance).

answered Oct 07 '15 at 20:56

Victor - Reinstate Monica

1,264
9
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How to check if a number that starts with a letter

2 Answers2