base58 encoder and decoder for js

base58.js

const base58Chars = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
const base58Table = {...Object.fromEntries(Object.entries(base58Chars).map(([k,v])=>[v,BigInt(k)])),...base58Chars}

/** @param {arrayBuffer} buf */
function base58enc(buf){
    const u8 = new Uint8Array(buf)
    let int = 0n
    u8.forEach( (x,i) => int += BigInt(x * 256 ** (u8.length-1-i)) )
    let res = ""
    while (1){
        const [x,y] = [int%58n,int/=58n]
        res = base58Table[x] + res
        if (!y)return res
    }
}

/** @param {string} value */
function base58dec(value){
    const u8 = []
    let int = 0n;
    [...value].forEach( (x,i) => int += base58Table[x] * BigInt(58 ** (value.length-1-i)) )
    while (1){
        const [x,y] = [int%256n,int/=256n] 
        u8.unshift(Number(x))
        if (!y)return new Uint8Array(u8).buffer
    }
}