Generating a seed: a general approach

IOTA101_67D98D069B61.js

// The snippet is a part of the IOTA Developer Essentials project. You can reach it at https://hribek25.github.io/IOTA101/
// Complete description and story behind the snippet is available at: https://hribek25.github.io/IOTA101/Allchapters_javascript.ipynb.html#67D98D069B61

//based on https://gist.github.com/SteveFromTheOffice/c8448a09352337386f135a16bbb20d93
//modified by Petr Zizka
    
var GenerateSeed = function () {
    const length       = 81;                            // The length of the seed and int array.
    const chars        = "ABCDEFGHIJKLMNOPQRSTUVWXYZ9"; // The allowed characters in the seed.
    var result       = new Array(length);               // An empty array to store the seed characters.
    var randomValues = Buffer.alloc(length)
    
    // Generate random values and store them to array.
    crypto.randomFillSync(randomValues);
    
    var cursor = 0;                                     // A cursor is introduced to remove modulus bias.
    for (var i = 0; i < randomValues.length; i++) {     // Loop through each of the 81 random values.
        cursor += randomValues[i];                      // Add them to the cursor.
        result[i] = chars[cursor % chars.length];       // Assign a new character to the seed based on cursor mod 81.
    }
    return result.join('');                             // Merge the array into a single string and return it.
};

var NewSeed = GenerateSeed();
console.log(NewSeed);
console.log("Length: %s", NewSeed.length)