Legal ID

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Function

verifyIranianLegalId(legalId: string | number): boolean | undefined

import { verifyIranianLegalId } from "@persian-tools/persian-tools";

verifyIranianLegalId("10380284790"); // true
verifyIranianLegalId(10380284790); // true (number accepted)
verifyIranianLegalId("00000000000"); // false (all zeros)
verifyIranianLegalId(undefined as any); // undefined

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Algorithm

1. Falsy input → undefined.
2. Stringify; length must be ≥ 11.
3. Reject if parseInt(legalId) === 0.
4. Reject if the middle 6 digits (slice(3, 9)) are all zero.
5. Compute check digit with coefficient vector [29, 27, 23, 19, 17] (cycled per period of 5):
   d   = digit[9] + 2
   sum = Σ (d + digit[i]) * z[i mod 5]  for i in 0..9
   sum = sum mod 11
   if sum === 10, sum = 0
   valid = digit[10] === sum
   

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Pitfalls

• Length check is < 11, not === 11. Inputs longer than 11 chars are accepted; the algorithm slices fixed indices, so longer strings can still validate. If you need strict 11-digit input, check String(input).length === 11 separately.
• Persian/Arabic digit input is not normalized. parseInt("۱۰۳۸۰۲۸۴۷۹۰") is NaN. Run autoConvertDigitsToEN first.
• Return type is boolean | undefined — use === true, not truthy.
• For personal IDs (10 digits, different algorithm), use verifyIranianNationalId.

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Source