Regular Expression text insertion in javascript

Question

I have some string that could be on a URL.. ala.. I can "get the name/value" etc.. that is not the issue. The issue is that given some test I need to "insert" additional characters in the value. so:

var someValue = "yes_maybe_next_year"

If I get a string with "_maybe" in it, I would insert my additional chars after it, ala. so it would become:

var charsToInsert = "_no";
var someValue = "yes_maybe_next_year";
var newValue = "yes_maybe_no_next_year";

Here is the rub. I might not get "maybe" in there. So I need to insert "_no" after "yes". Here is a second rub. The string might contain chars that are different than "next_year".

var someValue = "yes_sometime_later";

So, in truth: I need to be able to insert via regex something like.

var regex = /^(yes_)(maybe_)(\w*)?/

I'm actually at a loss on how to do this.

So, if "maybe_" exists, I'll put "no" after it, else "no" goes after "yes_".

If you use conditions, good practice to do it in 2 steps: if .. else. Regex is pretty expensive in your case. Its seems good to do it with 1 row but ... :) — Maxim Shoustin
– Maxim Shoustin, Commented Feb 20, 2013 at 9:04

VisioN · Accepted Answer · 2013-02-20 09:03:36Z

3

Here is one possible solution:

var newValue = someValue.replace(/yes_(maybe_)?/, "$&no_");

// "yes_maybe_next_year" --> "yes_maybe_no_next_year"
// "yes_sometime_later"  --> "yes_no_sometime_later"

answered Feb 20, 2013 at 9:03

VisioN

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2 Comments

james emanon Over a year ago

yeah, after goofing around, I came up with this: .replace(/^(yes_)(maybe_)?/, "$1$2no_") ---> what does your $& do?

james emanon Over a year ago

@VisionN - so in this case it would be short for my "$1$2"?

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