Regex Puzzle

[Twey]

I have a slight problem. I have a string, in which I want to match /\\e\[([^m]+)m/g, and replace it with a value pulled out of an array, the index of which should be \1. Is this even possible? The problem is that String.replace() doesn't parse \# until it's actually called, and the value needs to be taken from the array before the call happens. For this reason I don't think it can be done. Can anyone suggest an alternative approach?

[mwinter]

I have a string, in which I want to match /\\e\[([^m]+)m/g, and replace it with a value pulled out of an array, the index of which should be \1.

Just to clarify, Twey, you have a string that may contain one or more sequences in a string that would match \e[XXm where XX is a number[1], and you want to replace that entire sequence with the value from the array with the aforementioned numeric index?

Is this even possible?

Yes.

The problem is that String.replace() doesn't parse \# until it's actually called, and the value needs to be taken from the array before the call happens.

When using a string for the second argument, yes. It's simple, though, using a function argument:

string.replace(/\\e\[([^m]+)m/g, function(match, index) {
  return array[index];
});

Unfortunately, some browsers (such as IE5) won't support this, so you might need to take a completely different approach:

var pattern = /\\e\[([^m]+)m/g,
    result  = '',
    index   = 0,
    matches;

while((matches = pattern.exec(string))) {
  result += string.substring(index, matches.index)
          + array[matches[1]];
  index   = pattern.lastIndex;
}
result += string.substring(index);

Mike


[1] I assume it's a number, otherwise an array is inappropriate and an object (literal) would be better (and might do anyway). Moreover, if it is a number, then [^m] could be replaced with \d.

[Twey]

Aha! Brilliance. Thank you, Mike, that was exactly what I was after