Javascript split string in different sized substrings

Question

I need to code an algo that, giving a hex string,generates an array with 5 elements of 4 hex digits and another array with 2 elemetents of 2 hex digits long. The unique two premises are:

• if the 4 digit string is = "0000" don't take it into account and if the 2 digit long hex is "00" (EDIT: or "01") don't take it into account neither.
• don't use the digits used for the five 4char strings for the 2char strings. I don't mind if one starts form the beginning and the other one from the end or the middle, or both from the middle...i mean the substrings don't need to be consecutive, they just have to be different from 0 and same string positions not used in both arrays. Edit: Imagine that the five 4char sequences are built using the first 20 characters (there is no "0000" sequence after splitting the main string every four chars). That means that the two 2char sequences don't have to take into account the first 20 chars as they have already been used.

Example of one correct output:

String : 87b86156d0000a4200005e02002f56614f7a2f54f7ebf45670ed62cbaa78e6f228297b0e7338215fb4

first array: ["87b8", "6156", "d000", "0a42", "5e02"]

second array: ["2f", "56"]

My approach starts like this:

var mystring = "87b86156d0970a4200005e02612f56614f7a2f54f7ebf45670ed62cbaa78e6f228297b0e7338215fb4"
var firststring = mystring.match(/.{1,4}/g);

Which gives me:

["87b8", "6156", "d097", "0a42", "0000", ...]

then:

for (x=0;x<firststring.length;x++){
        if (firststring[x]=="0000") {firststring.splice(x, 1)}
}

  var secondstring = mystring.match(/.{1,2}/g);

Which gives me:

["87", "b8", "61", "56", "d0", "97"...]

for (x=0;x<secondstring.length;x++){
        if (secondstring[x]=="00") {secondstring.splice(x, 1)}
}

Here is where i am lost, i don't know exactly how to code the part where i avoid the main string digits (positions) to be used in both arrays...

Regards,

Answer 1

Well, it's not pretty, but it works:

var str = "87b86156d0970a4200005e02612f56614f7a2f54f7ebf45670ed62cbaa78e6f228297b0e7338215fb4";

var grabLength = 4,
    // 4-char strings
    grp1 = [],
    // 2-char strings
    grp2 = [],
    chunk;

while(chunk = str.slice(0, grabLength)) {
  str = str.slice(grabLength);

  // skip all zeros
  if (/^0+$/.test(chunk)) continue;

  if (grabLength === 4) {
    if (grp1.push(chunk) === 5) {
      grabLength = 2;
    }
    continue;
  }

  // skip 2-char sequences that match the start of a 4-char sequence
  var hasMatch = false;
  for (var i = 0; i < grp1.length; i++) {
    if (chunk === grp1[i].slice(0, 2)) {
      hasMatch = true;
      continue;
    }
  }
  if (hasMatch) continue;

  grp2.push(chunk);

  if (grp2.length === 2) break;
}

console.log(grp1);
console.log(grp2);

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