Grunt: replace wildcard value when using grunt-text-replace - regex

Question

I'm no regex master, and I'm pretty sure a regex is what is needed in this instance.
I currently have a text replacement task like so:
configSeed: {
src: ['src/*/local/app-config.js'],
overwrite: true,
replacements: [
{
from: 'var CONFIG_SEED_STRING = null;',
to: 'var CONFIG_SEED_STRING = "{"some_stringified_dynamic_json":"values"}";'
}
]
}
Which works fine the first time the config file is saved, the above string is replaced.
However, as soon as the string is replaced, further changes to the config don't have a replacement applied because obviously null is no longer to be found.
null is where my wildcard value needs to be, and the value could be either null (initially) or subsequent replacing a valid JSON string instead.
If my assumption about a wildcard being needed is true, would that trigger recursion upon save? Or does Grunt have in-built protection against this situation? [edit: I've tested this by replacing the string with the same value, recursion does not occur.]
So, assuming it is safe to use a wildcard where I want to, could I please get help with a regex value to be replaced?
Alternative solutions also welcome, for example my code base is unchanging enough that I could viably replace a line of code completely, if that's possible.
Thanks for any help provided.

Answer 1

Omg, I actually did it, what a feeling. After some painful reading on regex again:
configSeed: {
src: ['src/*/local/app.js'],
overwrite: true,
replacements: [
{
from: /var CONFIG_SEED_STRING = '[^']*'/g,
to: 'var CONFIG_SEED_STRING = \'{"foo":"bar"}\''
},
{
from: 'var CONFIG_SEED_STRING = null',
to: 'var CONFIG_SEED_STRING = \'{"foo":"bar"}\''
}
]
}
Not perfect, because I have two from/tos, but it catches both null and valid JSON data in between single quoted String value for CONFIG_SEED_STRING.
Instant reward time for writing a regex! I'm allowing myself 15 minutes of Youtube at work.