Generating alphanumerical sequence javascript

Question

I have written a terribly slow function for generating codes that go from AA000 to ZZ999 (in sequence not random). And I have concluded that there has to be a better way to do this. Any suggestions on how to make this faster?

function generateAlphaNumeric(){

theAlphabet = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'];
resultArrray = [];
resultArrray2 = [];
teller = 0;

for(i in theAlphabet){
    for(x in theAlphabet){
        resultArrray[teller] = theAlphabet[i] + theAlphabet[x];
        teller++;
    }
}
teller = 0;
for(x = 0; x<10; x++){
    for(y = 0; y<10; y++){
        for(z = 0; z<10; z++){
            resultArrray2[teller] = x.toString() + y.toString() +z.toString();
            teller++;
        }
    }
}
teller = 0;
finalArray = [];
for(index in resultArrray){
    for(i in resultArrray2){
        finalArray[teller] = resultArrray[index] + resultArrray2[i];
        teller++;
    }
}
//console.log(resultArrray);
//console.log(resultArrray2);
console.log(finalArray);
}

Answer 1

This should be considerably faster:

var theAlphabet = ['A','B','C','D','E','F','G','H','I','J','K','L','M','N','O',
'P','Q','R','S','T','U','V','W','X','Y','Z'];
var theDigits = ['0','1','2','3','4','5','6','7','8','9'];

var result = [];
for (var i=0 ; i<26 ; i++) {
    var prefix1 = theAlphabet[i];
    for (var j=0 ; j<26; j++) {
        var prefix2 = prefix1 + theAlphabet[j];
        for(var x = 0; x<10; x++){
            var prefix3 = prefix2 + theDigits[x];
            for(var y = 0; y<10; y++){
                var prefix4 = prefix3 + theDigits[y];
                for(var z = 0; z<10; z++){
                   result.push(prefix4 + theDigits[z]);
                }
            }       
        }
    }
}

Key ideas:

• Generate everything in one run
• Reuse partial strings as much as possible

However, I don't see how such an exhaustive list is useful. There are exactly 26 * 26 * 1000 different codes. So instead of maintaining an array with all codes it could make sense to simply build a function that generates the specific code requested:

function getCode(number) {
    var z = number % 10;
    number -= z; number /= 10;
    var y = number % 10;
    number -= y; number /= 10;
    var x = number % 10;
    number -= x; number /= 10;
    var a = number % 26;
    number -= a; number /= 26;
    var b = number;

    return theAlphabet[a] + theAlphabet[b] + theDigits[x] + theDigits[y] + theDigits[z];
}