Javascript - How can I use hexadecimal values as array keys?

Question

The Problem
Only HEX values of 10 through ff work. I can not assign 00 through 0f as keys; they get dropped from it seems. My understanding is that these values would require quotes to work, but that doesn't seem to be the case. I even read this article and it didn't help. How can I assign these HEX values as array keys?

Background
What I am trying to do is create a substitution array that holds HEX values that will be used to substitute other HEX values. Confusing? Let me show you:

This HEX string comes in (Text that was changed to HEX): 2a2b

My goal is then to use the substitution array to change this into another hex string like so: 1fa9

The fastest way I can think to do this is to assign HEX values to the array keys this way I can look up the key that matches the hex value and substitute it right away for its value like so:

// I'm working with chunks of 25 fyi
for (var i = 0; i < 25; i++) {
  dataChunck[i] = substitueArray[dataChunck[i]];
}

The Rest of My Code
This has been cut down to just what you need. hexValues is an array of HEX values 00 through ff.

// Start at array index 1 because be defined and saved 0 already
for (var x = 1; x < 256; x++) {
  if (counter > 255) {
    break; // We now have all 256 HEX values, stop
  }
  // We want to allow 256 as an option so go 1 higher (257)
  if (sub > 0 && sub < 257) {
    // If the number (HEX value) is not already saved save it
    if (sboxValues.indexOf(hexValues[sub - 1]) < 0) {
      // RIGHT HERE IS THE PROBLEM!!!
      // This assigns a HEX value as the key and saves sub to it
      // sub as you can see gets converted to HEX as its saved
      sboxValues[hexValues[x]] = hexValues[sub - 1];
      counter++;
    } else {
      // Glitch: That number has been saved, redo this round
      // Keep x on track so we don't accidently reuse it
      x--;
    }
    sub += num; // Move on to new number
  } else {
    // Removed. You don't need to see this code
    // Keeps x on track so we don't accidently reuse it
  }
}

Jon · Accepted Answer · 2015-01-24 23:02:06Z

2

What you are trying to do is have string keys in an array. That is not possible.

What you could do instead is use a plain object as a map (instead of an array) or else just convert the hex strings you would like to use as keys into their decimal representations with parseInt, e.g.:

sboxValues[parseInt(hexValues[x], 16)] = hexValues[sub - 1];

answered Jan 24, 2015 at 23:02

Jon

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3 Comments

Blizzardengle Over a year ago

I was thinking of going the decimal route as well. I am not strong in Javascript though, PHP is more my thing. So the code you put is saving a decimal key of the HEX value correct?

Jon Over a year ago

@Blizzardengle: Yes, but the best way to know is to try it ;-)

Blizzardengle Over a year ago

Of course. Thanks so much for this answer. I was originally testing changing whole chunks of my code to manage decimals instead of HEX and never thought of doing it so simply. This saved me so much work.

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