Sequential strings javascript

Question

I'm stuck on sequential string generation, the last iteration of the code below, is trying to return ac.

var charcode = 'abcdefghijklmnopqrstuvwxyz0123456789_';
var arr = [];
var len = 1;
var current = 0;

for(var i = 0; i < 40; i++) {
    if(current == charcode.length) {
        current = 0
        len++
    }
    var tmpStr = ''
    for(var l = 0; l < len; l++) {
        tmpStr = tmpStr + charcode[current];
    }
    console.log(tmpStr)
    current++
}

However, it produces cc.

Sorry, somehow deleted the intended output

a, b, c ... aa, ab, ac ... ba, bc, bb ... ∞

My current understanding suggests within the l < len loop I should check if len > 1 and if so break out and loop for the current charcode[x] but I just can't wrap my head around breaking in and out as it grows.

Answer 1

You can do it like this:

var charcode = 'abcdefghijklmnopqrstuvwxyz0123456789_';
var arr = [];
var len = 0;
var current = 0;

for(var i = 0; i < 40; i++) {
  if(current == charcode.length) {
     current = 0;
     len++;
  }

  var tmpStr = (len===0) ? '' : charcode[len-1];

  tmpStr = tmpStr + charcode[current];
  current++;
  console.log(tmpStr);
}

In brief, you didn't need a second loop, but an iteration instead (which is achieved through charcode[len-1]).

JS Bin here.

UPDATE

If you need a continuos loop until the very end of the charset, you can use this:

This one introduces a third variable (digits) to the iteration and choses a .substr() instead of a single character out of the charset, so that everytime the end of the charset is reached, another digit will be added. The variable called x sets the limit. I have tried 4000 and it looks like it is working.

var charcode = 'abcdefghijklmnopqrstuvwxyz0123456789_',
    arr = [],
    len = 0,
    digits = 2,
    current = 0,
    tmpStr = '';

var x = 4000;

for(var i=0; i<x; i++) {
    if(current === charcode.length) {
        current = 0;
        len++;
        if(tmpStr.substr(0,1) === charcode.substr(-digits,1) || tmpStr === charcode.substr(-1) + '' + charcode.substr(-1)) {
            len = 1;
            digits++;
        }  
     }

     if(digits === charcode.length) {
         console.log(charcode);
         console.log(i + ' results found');
         break;
     }

     tmpStr = (len===0) ? '' : charcode.substr([len-1], digits-1);

     tmpStr += charcode[current];
     current++;
     console.log(tmpStr);
}

Final JS Bin here.