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I need to check if a geohash string is valid, so I need to check if it's a base32 or not.

  • Can you add some more content to this question, to show us what you've already tried to solve this problem, and what issues you've run into? – Rob Wilkins Dec 03 '18 at 21:29
  • This answer is not perfect, but the better I've found https://stackoverflow.com/a/27362880/2093371 – hestellezg Jan 23 '21 at 06:49

2 Answers2

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Base32 uses A-Z and 2-7 for the encoding, and adds a padding character = to get a multiple of 8 characters, so you can create a regex to see if the candidate string matches.

Using regex.exec a matching string will return the match information, a non-matching string will return null, so you can use an if to test whether a match is true or false.

Base32 encodings also must always be a length that is a multiple of 8, and are padded with enough = chars to make it so; you can check the length is correct by using mod 8 --
if (str.length % 8 === 0) { /* then ok */ }

// A-Z and 2-7 repeated, with optional `=` at the end
let b32_regex = /^[A-Z2-7]+=*$/;

var b32_yes = 'AJU3JX7ZIA54EZQ=';
var b32_no  = 'klajcii298slja018alksdjl';
    
if (b32_yes.length % 8 === 0 &&
    b32_regex.exec(b32_yes)) {
    console.log("this one is base32");
}
else {
    console.log("this one is NOT base32");
}
    
if (b32_no % 8 === 0 &&
    b32_regex.exec(b32_no)) {
    console.log("this one is base32");
}
else {
    console.log("this one is NOT base32");
}
Stephen P
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    Don't forget the padding character '='! `/^[A-Z2-7=]+$/` – Zim Dec 03 '18 at 20:12
  • Thanks @Zim — updated to include optional padding. Length checks could also be done, since the length must be a multiple of 8 `b32_yes % 8 === 0 and b32_regex.exec(...)` – Stephen P Dec 03 '18 at 20:42
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function isBase32(input) {
    const regex = /^([A-Z2-7=]{8})+$/
    return regex.test(input)
}

console.log(isBase32('ABCDE23=')) //true
console.log(isBase32('aBCDE23=')) //false

console.log(isBase32('')) //false
console.log(isBase32()) //false
console.log(isBase32(null)) //false

console.log(isBase32('ABCDE567ABCDE2==')) //true
console.log(isBase32('NFGH@#$aBCDE23==')) //false
Anderson Oliveira Martins
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