How to retrieve a substring and replace it with a random value it contains?

Let’s say I have a string like this:

This is just a test {#3,2,7,9} this is another test {#21,2,11}

How can I retrieve all instances of {#x,y,..} and replace it with a random number it contains?

For example, the string above could become:

This is just a test 2 this is another test 11

>Solution :

Try using replace() method

Regex Demo

https://regex101.com/r/s3O59z/1

let string = 'This is just a test {#3,2,7,9} this is another test {#21,2,11}'

let result = string.replace(/{#(.*?)}/g, (match, p1) => {
  let nums = p1.split(',')
  return nums[Math.floor(Math.random() * nums.length)]
})

console.log(result)