Expressions & JSON Cheat Sheet

WDL is not Power Fx

Cloud-flow expressions use the Workflow Definition Language (shared with Azure Logic Apps), not Power Fx. Functions are prefix-style — add(1,2), not 1 + 2 — and reference runtime data with triggerBody(), body('Action'), outputs('Action'), variables('x'), and items('Apply_to_each'). The same reference exists for Azure Logic Apps and Power Automate.

Reference functions — reaching runtime data

Before any other function, you need a handle on the data flowing through the run. These functions pull values out of the trigger, prior actions, loops, variables, and the run itself. Most are *shorthands* — body('X') is just outputs('X')?['body'], and triggerBody() is trigger().outputs.body.

String functions

Encoding & conversion

Collection & array functions

Logical & comparison

Date & time

JSON & objects

json(variables('rawString'))                       // string -> object
outputs('Compose')?['data']?['id']                  // null-safe read
addProperty(variables('obj'), 'status', 'open')     // add a key
setProperty(variables('obj'), 'status', 'closed')   // overwrite a key
removeProperty(variables('obj'), 'temp')            // drop a key
xpath(xml(body('HTTP')), '//Order/Id/text()')       // query XML

{
  "name": "@item()?['displayName']",
  "email": "@item()?['mail']"
}

XML & xpath deep-dive

When a connector hands back XML (legacy SOAP, RSS, some HTTP APIs), convert it with xml() first, then query with xpath(). xpath returns an array of matches, so wrap single-value reads in first(). Use /text() to get the inner value rather than the node.

// single value (note: xpath returns an array)
first(xpath(xml(body('HTTP')), '//Order/Id/text()'))

// all matching values as an array
xpath(xml(body('HTTP')), '//Order/LineItem/Sku/text()')

// an attribute
first(xpath(xml(body('HTTP')), 'string(//Order/@status)'))

// count of nodes
xpath(xml(body('HTTP')), 'count(//Order/LineItem)')

Array cookbook

Reshape, filter, and aggregate arrays without an Apply to each wherever you can — Select and Filter array run server-side and are far faster than a loop.

Reshape objects with a Select action

{
  "id": "@item()?['ID']",
  "title": "@item()?['Title']",
  "owner": "@item()?['Author']?['DisplayName']"
}

Filter array — advanced (query) syntax

@and(equals(item()?['Status'], 'Active'), greater(item()?['Amount'], 1000))

Dedupe a flat array

union(variables('tags'), variables('tags'))

Pull one column, then dedupe (group-by keys)

// Select (text/code) outputs an array of department strings:
@item()?['Department']

// then on that output:
union(body('Select_departments'), body('Select_departments'))

Flatten an array of arrays

union(variables('listA'), variables('listB'))

Build an Adaptive Card payload from rows

{
  "type": "TextBlock",
  "text": "@{item()?['Title']} — @{item()?['Status']}",
  "wrap": true
}

Date cookbook

Start and end of the current month

startOfMonth(utcNow())                                           // first day, 00:00
addDays(startOfMonth(addToTime(utcNow(), 1, 'Month')), -1)       // last day of this month

Business days between two dates (approx)

sub(
  div(sub(ticks(variables('end')), ticks(variables('start'))), 864000000000),
  mul(2, div(div(sub(ticks(variables('end')), ticks(variables('start'))), 864000000000), 7))
)

Age in whole years

div(sub(ticks(utcNow()), ticks(variables('dob'))), 315360000000000)

Next occurrence of a weekday (e.g. next Monday)

addDays(startOfDay(utcNow()), add(mod(sub(8, dayOfWeek(utcNow())), 7), if(equals(dayOfWeek(utcNow()), 1), 7, 0)))

Calendar quarter (1–4)

add(div(sub(int(formatDateTime(utcNow(), 'MM')), 1), 3), 1)

Relative timestamps

getPastTime(24, 'Hour')        // 24h ago, ISO 8601
getFutureTime(2, 'Week')       // 2 weeks out
subtractFromTime(utcNow(), 30, 'Day')

JSON cookbook

Safe deep access with a default

coalesce(body('HTTP')?['data']?['user']?['email'], 'unknown@contoso.com')

Build a nested object inline

json(concat('{"id":', variables('id'), ',"name":"', variables('name'), '"}'))

Merge two objects (shallow)

union(variables('defaults'), variables('overrides'))

Add a property only when a condition holds

if(empty(variables('note')),
   variables('payload'),
   addProperty(variables('payload'), 'note', variables('note')))

Escape a value for embedding in JSON text

replace(replace(variables('text'), '\\', '\\\\'), '"', '\\"')

No native regex in WDL

There is no regular-expression function in cloud-flow expressions. Most validation and extraction can still be done with the string primitives — and for anything heavier, push the work to a tool that does have regex.

• Contains / matches — contains(), startsWith(), endsWith() cover prefix/suffix/substring checks.
• Extract between markers — combine indexOf() / nthIndexOf() / lastIndexOf() with substring() or slice().
• Tokenize — split() on a delimiter, then index into the resulting array.
• Real regex — call an Office Scripts action (Excel) or a small Azure Function, both of which run JavaScript/.NET regex.
• Fuzzy / semantic matching — AI Builder or a model action when the pattern isn't strictly lexical.

slice(
  triggerBody()?['text'],
  add(indexOf(triggerBody()?['text'], '('), 1),
  indexOf(triggerBody()?['text'], ')')
)

Common patterns

Real expressions that nest several functions — paste into the expression editor and swap the references for your own.

Days between two dates

div(sub(ticks(variables('endDate')), ticks(variables('startDate'))), 864000000000)

Now, formatted in local time

formatDateTime(convertTimeZone(utcNow(), 'UTC', 'Eastern Standard Time'), 'yyyy-MM-dd HH:mm')

Safe nested read with a fallback

coalesce(body('HTTP')?['data']?['email'], 'no-email@contoso.com')

First name from a full name

first(split(triggerBody()?['name'], ' '))

Timestamped file name

concat('export-', formatDateTime(utcNow(), 'yyyyMMdd-HHmmss'), '.csv')

Inline if / else (ternary)

if(greater(int(triggerBody()?['amount']), 1000), 'High', 'Standard')

Percentage complete as text

concat(formatNumber(div(mul(float(variables('done')), 100), float(variables('total'))), 'F1'), '%')

Weekend check

or(equals(dayOfWeek(utcNow()), 0), equals(dayOfWeek(utcNow()), 6))

Normalize then compare (trim + lowercase)

equals(toLower(trim(triggerBody()?['email'])), 'admin@contoso.com')

Empty-safe join of an array

if(empty(variables('tags')), 'none', join(variables('tags'), ', '))

Domain from an email address

last(split(triggerBody()?['email'], '@'))

File extension (lowercased)

toLower(last(split(triggerBody()?['fileName'], '.')))

Pad a number to 4 digits

slice(concat('0000', string(variables('seq'))), -4)

Title-case the first letter of a word

concat(toUpper(substring(variables('w'), 0, 1)), toLower(substring(variables('w'), 1)))

Strip the query string from a URL

if(contains(variables('url'), '?'), first(split(variables('url'), '?')), variables('url'))

Pluralize a label by count

concat(string(variables('n')), ' item', if(equals(variables('n'), 1), '', 's'))

Build a mailto link

concat('mailto:', variables('to'), '?subject=', uriComponent(variables('subject')))

Minutes as h:mm

concat(string(div(variables('mins'), 60)), ':', slice(concat('0', string(mod(variables('mins'), 60))), -2))

Clamp a number into a range

max(0, min(100, variables('score')))

Common gotchas

• No `dateDiff()` — subtract ticks() and divide (days = 864000000000, hours = 36000000000, minutes = 600000000).
• `dayOfWeek` Sunday is `0`, not `7` — weekend test: or(equals(dayOfWeek(d),0), equals(dayOfWeek(d),6)).
• No regex — use indexOf / split / slice, or offload to Office Scripts / AI Builder.
• `body()` is not `outputs()` — most connector payloads live under body; outputs(...)?['body'] is the long form of body(...).
• `xpath` returns an array — wrap single reads in first(), and watch for default XML namespaces breaking plain //Node paths.
• Float math drifts — use decimal() for currency; div() on two integers truncates, so cast to float() first.
• Strings vs interpolation — in a text field use @{expression}; a field that is *only* an expression uses a leading @.
• Parse JSON nulls — make optional properties nullable in the schema or the action fails on a missing field.
• Apply to each is slow — enable concurrency (Settings) for independent iterations, or replace the loop with Select / Filter array where possible.