Flow - character replace pattern with chunk()

Hi, it’s 5am, I can’t sleep, I had these two Flow ideas that are really cool.

First is a super fun trick with

• chunk()

• Select

• join()

• coalesce()

No loops.
No variables.

First problem - string character replacement - safe HTML normaliser

Let’s start with this string

Now imagine this text is:

• coming from Dataverse

• pasted by a user

• generated by AI

• injected into HTML email

• rendered inside a PDF

If you don’t escape it properly… things break.

We want to safely replace:

Character	Replace With
<	<
>	>
"	"
'	’ (optional smart quote)

Power Automate doesn’t give us a multi-replace expression. You’ve probably done this type of replace-replace before

replace(
      replace(
        replace(
          replace(
            replace(
              string(outputs('Compose')),
              '&','&'
            ),
            '<','<'
          ),
          '>','>'
        ),
        '"','"'
      ),
      '''','''
    )

So the clever hack I have is this:

1. Use chunk to break string into char array

chunk(outputs(‘Compose’),1)

2. Use Select action to map this array with a formula that replaces certain characters

We are testing each character in order:

1. If < → return <

2. If > → return >

3. If " → return "

4. If ' → return ’

5. Otherwise → return original character

coalesce() returns the first non-null value.

3. join it back together

join(body(‘Select’),”)

Why not just use Replace?

You could chain:

replace(replace(replace(...)))

But:

• It becomes unreadable fast

• Order matters (you can double-encode)

• It doesn’t scale well

• It’s painful to debug

Using chunk() + Select():

• You see exactly what happens per character

• It’s safe

• It’s predictable

• It’s extensible

It’s basically a mini parsing engine.

The Hidden Insight

The real trick isn’t escaping characters.
The trick is this:

Turn string → array → transform → join.

Once you realise Select is a map function…