CPF is the Individual Taxpayer Registry is the register maintained by the Federal Revenue of Brazil in which any natural persons, regardless of age or nationality, including those who have died, can register once. Each registrant is uniquely identified by an 11 decimal digitCPF registration number. more Obs:. It's the Brazilian link.
The algorithm to say if the CPF is valid is quite simple. As we know every CPF has 11 digits like this 13255042895, so the whole logic behind the CPF is based in the two last numbers of that we call validation digits, we need to make two series ofcalculations and if the results(validation digits) are equal to the two last digits of CPF so it's valid.
1 3 2 5 5 0 4 2 8
and multiply by this sequence
10 9 8 7 6 5 4 3 2
| 1 | 3 | 2 | 5 | 5 | 0 | 4 | 2 | 8 |
|---|---|---|---|---|---|---|---|---|
| x | x | x | x | x | x | x | x | x |
| 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 |
result of multiplication
| 10 | + | 27 | + | 16 | + | 35 | + | 30 | + | 0 | + | 16 | + | 6 | + | 16 | = | 156 |
|---|
after sum the values we need to divide them by 11, if the remainer is lower than 2 the firts validation digits it's 0 else, than we devide the sum by 11 and subtract the remainer by subtract 11.
Firts validate digit is 9 and it's matches.
for the seconde calculation is basicaly the same thing, only some changes as you can see.
1 3 2 5 5 0 4 2 8 9
and multiply by this sequence
11 10 9 8 7 6 5 4 3 2
| 1 | 3 | 2 | 5 | 5 | 0 | 4 | 2 | 8 | 9 |
|---|---|---|---|---|---|---|---|---|---|
| x | x | x | x | x | x | x | x | x | x |
| 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 |
result of multiplication
| 11 | + | 30 | + | 18 | + | 40 | + | 35 | + | 0 | + | 20 | + | 8 | + | 24 | + | 18 | = | 204 |
|---|
Second validate digit is 5 and it's matches too so the CPF is valid.
Obs:. There some examples of types of CPF that are not assigned by anybody.
| 000.000.0000-00 | 111.111.111-11 | 222.222.222-22 | 333.333.333-33 |
|---|---|---|---|
| 444.444.444-44 | 555.555.555-55 | 666.666.666-66 | 777.777.777-77 |
| 888.888.888-88 | 999.999.999-99 | 111.234.111-75 | 111.234.361-11 |
| 881.111.118-88 | 999.991.111-11 | 111.111.361-75 |
I made this very noobie RegEx to catch all the possible wrong CPF.
const RegEx = [
/(^[A-ZÀ-Ú-a-zà-ú_@/#&+*]*$)/,
/([(1){6}]{6})|([(2){6}]{6})|([(3){6}]{6})|([(4){6}]{6})|([(5){6}]{6})|([(6){6}]{6})|([(7){6}]{6})|([(8){6}]{6})|([(9){6}]{6})|([(0){6}]{6})/g
];
if(cpf.match(RegEx[1]) || cpf.length < 11) ? "CPF invalid!" : "CPF algorithm";