Automatically replace argument in RegEx JavaScript

Question

I have a question about some regular expressions.

For context, I'm currently creating Custom Commands on a Discord bot. I need to re-arrange arguments in the command.

I have this string here - bin [user] [aRG] [arg] [DEsc] and need to arrange it like so - bin [USER] $0 $1 [DESC]. I also need to make it case insensitive.

I tried to create IF statements on every possible occasion. But what I also need to keep in mind, is that I need to re-arrange it if the [DESC] comes in first then the arguments. This is what I had -

let theString = "bin [uSER] [arg] [DESc] [ARg]";
let CmdName   = theString.split(" ")[0].toLowerCase();

if (theString.includes(/\[user\]/i)) CmdName += " [USER]";
if (theString.includes(/\[arg\]/i))  CmdName += " $0";
if (theString.includes(/\[arg\]/i))  CmdName += " $1";
if (theString.includes(/\[arg\]/i))  CmdName += " $2";
if (theString.includes(/\[desc\]/i)) CmdName += " [DESC]";

The above example wouldn't work anyways, if there is even one [ARG] in theString, it would include $0 $1 $2 in the CmdName variable because theString would never change.

In the above example, CmdName would need to end up like bin [USER] $0 $1 [DESC].

How can I do this effectively, possibly also iterating through it? Limiting the [ARG] value uses to three or four would also be handy.

adiga · Accepted Answer · 2019-05-01 13:38:04Z

1

You could use the regex \[(.*?)\] to to get the contents within [] to a capturing group (Regex demo). Then use a replacement function to handle for arg and other arguments separately. Use an argCounter to get consecutive numbers $0, $1

let str = "bin [user] [aRG] [arg] [DEsc]",
    argCounter = 0;

const newStr = str.replace(/\[(.*?)\]/g,
  (m, p1) => {
    if (p1.toUpperCase() === 'ARG')
      return `$${argCounter++}`
    else
      return `[${p1.toUpperCase()}]`
  })

console.log(newStr)

answered May 1, 2019 at 13:38

adiga

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Comments

jmcgriz · Accepted Answer · 2019-05-01 16:13:06Z

I'm not entirely following what you're trying to do, but regex might not be your friend here. I'd suggest splitting your command and looping through the resulting array. Something along these lines should get you where you're trying to go.

let theString = "bin [uSER] [arg] [DESc] [ARg]",
  stringSplit = theString.split(" "),
  cmd = stringSplit.shift(), //remove the command and store it
  arr = stringSplit.join(" ").toUpperCase().split(" ") //make the rest uppercase

let descIdx = arr.indexOf('[DESC]'),
  descStr = descIdx > -1 ? arr.splice(descIdx, 1) : "",
  userIdx = arr.indexOf('[USER]'),
  userStr = userIdx > -1 ? arr.splice(userIdx, 1) : ""
  
//now all that's left is the [ARG]s
let argStr = arr.map((arg, i) => ['$', i].join("")).join(" ")

//wrap it all up

let result = [cmd, userStr, argStr, descStr].join(" ")

console.log(result)

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