Q:

Angular 2+ textarea placeholder conditioned and with translate

conditioned:
<textarea
    class="form-control"
    [placeholder]="(i < 3) ? 'a' : 'b'">
</textarea>

a a a b b b b b b b b b
with translate:
<textarea
    class="form-control"
    placeholder="{{'STEPS.PLACEHOLDER' | translate}} {{title$ | async}}"
</textarea>

Title is foo
but I need conditioned and with translate:
<textarea
    class="form-control"
    ?placeholder?="?????"
</textarea>

1st title is foo
2nd title is foo
3th title is foo
next title is foo
next title is foo
next title is foo
next title is foo
next title is foo

A:

<textarea
    class="form-control"
    [placeholder]="(i < 3) ? ('STEPS.PLACEHOLDER_' + i | translate) + ' ' + (title$ | async) : ('STEPS.PLACEHOLDER_ELSE' | translate) + ' ' + (title$ | async)"
</textarea>

