Built-in Functions

TinySystems expressions support JavaScript built-in functions plus custom helpers. This reference covers all available functions.

String Functions

toUpperCase()

Convert string to uppercase:

yaml

data:
  upper: "{{$.name.toUpperCase()}}"
# "john" → "JOHN"

toLowerCase()

Convert string to lowercase:

yaml

data:
  lower: "{{$.name.toLowerCase()}}"
# "JOHN" → "john"

trim()

Remove whitespace from both ends:

yaml

data:
  trimmed: "{{$.input.trim()}}"
# "  hello  " → "hello"

trimStart() / trimEnd()

Remove whitespace from one end:

yaml

data:
  leftTrimmed: "{{$.input.trimStart()}}"
  rightTrimmed: "{{$.input.trimEnd()}}"

substring()

Extract part of a string:

yaml

data:
  sub: "{{$.text.substring(0, 5)}}"    # First 5 characters
  rest: "{{$.text.substring(5)}}"       # Everything after position 5

slice()

Similar to substring with negative index support:

yaml

data:
  first5: "{{$.text.slice(0, 5)}}"
  last3: "{{$.text.slice(-3)}}"

split()

Split string into array:

yaml

data:
  parts: "{{$.csv.split(',')}}"
  lines: "{{$.text.split('\\n')}}"

replace()

Replace occurrences:

yaml

data:
  replaced: "{{$.text.replace('old', 'new')}}"
  allReplaced: "{{$.text.replace(/old/g, 'new')}}"

includes()

Check if string contains substring:

yaml

data:
  hasWord: "{{$.text.includes('search')}}"

startsWith() / endsWith()

Check string boundaries:

yaml

data:
  startsWithHttp: "{{$.url.startsWith('http')}}"
  endsWithJson: "{{$.filename.endsWith('.json')}}"

padStart() / padEnd()

Pad string to length:

yaml

data:
  padded: "{{$.num.toString().padStart(5, '0')}}"
# "42" → "00042"

repeat()

Repeat string:

yaml

data:
  repeated: "{{$.char.repeat(3)}}"
# "x" → "xxx"

charAt()

Get character at position:

yaml

data:
  firstChar: "{{$.text.charAt(0)}}"

length

Get string length:

yaml

data:
  len: "{{$.text.length}}"

Number Functions

parseInt()

Parse string to integer:

yaml

data:
  num: "{{parseInt($.stringNum)}}"
  hex: "{{parseInt($.hexString, 16)}}"

parseFloat()

Parse string to float:

yaml

data:
  decimal: "{{parseFloat($.stringFloat)}}"

toFixed()

Format to fixed decimal places:

yaml

data:
  price: "{{$.amount.toFixed(2)}}"
# 19.5 → "19.50"

toString()

Convert to string:

yaml

data:
  str: "{{$.number.toString()}}"
  hex: "{{$.number.toString(16)}}"

isNaN()

Check if not a number:

yaml

data:
  valid: "{{!isNaN($.value)}}"

isFinite()

Check if finite number:

yaml

data:
  finite: "{{isFinite($.value)}}"

Math Functions

Math.round()

Round to nearest integer:

yaml

data:
  rounded: "{{Math.round($.value)}}"

Math.floor()

Round down:

yaml

data:
  floored: "{{Math.floor($.value)}}"

Math.ceil()

Round up:

yaml

data:
  ceiled: "{{Math.ceil($.value)}}"

Math.abs()

Absolute value:

yaml

data:
  absolute: "{{Math.abs($.value)}}"

Math.min() / Math.max()

Find minimum/maximum:

yaml

data:
  min: "{{Math.min($.a, $.b, $.c)}}"
  max: "{{Math.max(...$.values)}}"

Math.pow()

Exponentiation:

yaml

data:
  squared: "{{Math.pow($.value, 2)}}"
  # Or: "{{$.value ** 2}}"

Math.sqrt()

Square root:

yaml

data:
  sqrt: "{{Math.sqrt($.value)}}"

Math.random()

Random number (0-1):

yaml

data:
  random: "{{Math.random()}}"
  randomInt: "{{Math.floor(Math.random() * 100)}}"

Math.trunc()

Remove decimal part:

yaml

data:
  integer: "{{Math.trunc($.value)}}"

Math.sign()

Get sign (-1, 0, or 1):

yaml

data:
  sign: "{{Math.sign($.value)}}"

Array Functions

length

Get array length:

yaml

data:
  count: "{{$.items.length}}"

map()

Transform each element:

yaml

data:
  ids: "{{$.users.map(u => u.id)}}"
  doubled: "{{$.numbers.map(n => n * 2)}}"

filter()

Select matching elements:

yaml

data:
  active: "{{$.items.filter(i => i.active)}}"
  positive: "{{$.numbers.filter(n => n > 0)}}"

find()

Find first match:

yaml

data:
  admin: "{{$.users.find(u => u.role === 'admin')}}"

findIndex()

Find index of first match:

yaml

data:
  adminIndex: "{{$.users.findIndex(u => u.role === 'admin')}}"

some()

Check if any match:

yaml

data:
  hasAdmin: "{{$.users.some(u => u.role === 'admin')}}"

every()

Check if all match:

yaml

data:
  allActive: "{{$.users.every(u => u.active)}}"

reduce()

Aggregate values:

yaml

data:
  sum: "{{$.numbers.reduce((a, b) => a + b, 0)}}"
  grouped: "{{$.items.reduce((acc, item) => ({...acc, [item.type]: [...(acc[item.type] || []), item]}), {})}}"

sort()

Sort array:

yaml

data:
  sorted: "{{$.items.sort((a, b) => a.name.localeCompare(b.name))}}"
  byNum: "{{$.numbers.sort((a, b) => a - b)}}"

reverse()

Reverse array:

yaml

data:
  reversed: "{{$.items.reverse()}}"

slice()

Get subset:

yaml

data:
  first5: "{{$.items.slice(0, 5)}}"
  last3: "{{$.items.slice(-3)}}"

concat()

Combine arrays:

yaml

data:
  combined: "{{$.arr1.concat($.arr2)}}"

join()

Join to string:

yaml

data:
  csv: "{{$.items.join(',')}}"

includes()

Check if contains value:

yaml

data:
  hasValue: "{{$.items.includes('target')}}"

indexOf()

Find index of value:

yaml

data:
  index: "{{$.items.indexOf('target')}}"

flat()

Flatten nested arrays:

yaml

data:
  flattened: "{{$.nested.flat()}}"
  deepFlat: "{{$.deep.flat(Infinity)}}"

flatMap()

Map and flatten:

yaml

data:
  allTags: "{{$.items.flatMap(i => i.tags)}}"

Array.isArray()

Check if array:

yaml

data:
  isArr: "{{Array.isArray($.value)}}"

Array.from()

Create array from iterable:

yaml

data:
  arr: "{{Array.from($.set)}}"

Spread operator

yaml

data:
  unique: "{{[...new Set($.items)]}}"
  merged: "{{[...$.arr1, ...$.arr2]}}"

Object Functions

Object.keys()

Get object keys:

yaml

data:
  keys: "{{Object.keys($.obj)}}"

Object.values()

Get object values:

yaml

data:
  values: "{{Object.values($.obj)}}"

Object.entries()

Get key-value pairs:

yaml

data:
  entries: "{{Object.entries($.obj)}}"

Object.fromEntries()

Create object from pairs:

yaml

data:
  obj: "{{Object.fromEntries($.pairs)}}"

Object.assign()

Merge objects:

yaml

data:
  merged: "{{Object.assign({}, $.obj1, $.obj2)}}"

Spread operator

yaml

data:
  merged: "{{...$.defaults, ...$.overrides}}"
  extended: "{{...$.original, newField: 'value'}}"

hasOwnProperty()

Check property existence:

yaml

data:
  hasId: "{{$.obj.hasOwnProperty('id')}}"

Date Functions

Date.now()

Current timestamp (milliseconds):

yaml

data:
  timestamp: "{{Date.now()}}"

new Date()

Create date object:

yaml

data:
  date: "{{new Date()}}"
  fromTimestamp: "{{new Date($.timestamp)}}"
  fromString: "{{new Date($.dateString)}}"

toISOString()

ISO 8601 format:

yaml

data:
  iso: "{{new Date($.timestamp).toISOString()}}"

toLocaleDateString()

Locale date string:

yaml

data:
  local: "{{new Date($.timestamp).toLocaleDateString()}}"

getTime()

Get timestamp from date:

yaml

data:
  ms: "{{new Date($.dateString).getTime()}}"

Date.parse()

Parse date string to timestamp:

yaml

data:
  timestamp: "{{Date.parse($.dateString)}}"

JSON Functions

JSON.stringify()

Convert to JSON string:

yaml

data:
  json: "{{JSON.stringify($.obj)}}"
  pretty: "{{JSON.stringify($.obj, null, 2)}}"

JSON.parse()

Parse JSON string:

yaml

data:
  obj: "{{JSON.parse($.jsonString)}}"

Type Checking

typeof

Get type:

yaml

data:
  type: "{{typeof $.value}}"
  isString: "{{typeof $.value === 'string'}}"

instanceof

Check instance:

yaml

data:
  isDate: "{{$.value instanceof Date}}"
  isArray: "{{$.value instanceof Array}}"

Logical Operators

Ternary (?😃

yaml

data:
  result: "{{$.condition ? 'yes' : 'no'}}"

Nullish coalescing (??)

yaml

data:
  value: "{{$.value ?? 'default'}}"

Optional chaining (?.)

yaml

data:
  safe: "{{$.nested?.deeply?.value}}"

Logical OR (||)

yaml

data:
  fallback: "{{$.value || 'default'}}"

Logical AND (&&)

yaml

data:
  conditional: "{{$.enabled && $.value}}"

Comparison Operators

yaml

data:
  equal: "{{$.a === $.b}}"
  notEqual: "{{$.a !== $.b}}"
  greater: "{{$.a > $.b}}"
  greaterOrEqual: "{{$.a >= $.b}}"
  less: "{{$.a < $.b}}"
  lessOrEqual: "{{$.a <= $.b}}"

Function Reference Table

Category	Function	Description
String	`toUpperCase()`	Convert to uppercase
	`toLowerCase()`	Convert to lowercase
	`trim()`	Remove whitespace
	`split()`	Split into array
	`replace()`	Replace text
	`includes()`	Check contains
	`startsWith()`	Check prefix
	`substring()`	Extract portion
Number	`parseInt()`	Parse integer
	`parseFloat()`	Parse decimal
	`toFixed()`	Format decimals
Math	`Math.round()`	Round number
	`Math.floor()`	Round down
	`Math.ceil()`	Round up
	`Math.min()`	Find minimum
	`Math.max()`	Find maximum
	`Math.abs()`	Absolute value
Array	`map()`	Transform elements
	`filter()`	Select elements
	`reduce()`	Aggregate values
	`find()`	Find first match
	`sort()`	Order elements
	`slice()`	Get subset
	`join()`	Join to string
Object	`Object.keys()`	Get keys
	`Object.values()`	Get values
	`Object.entries()`	Get pairs
JSON	`JSON.stringify()`	To JSON string
	`JSON.parse()`	Parse JSON
Date	`Date.now()`	Current timestamp
	`toISOString()`	ISO format

Next Steps

Expression Syntax - Syntax reference
Data Transformation - Transformation patterns
Ports and Messages - Message structure

Built-in Functions ​

String Functions ​

toUpperCase() ​

toLowerCase() ​

trim() ​

trimStart() / trimEnd() ​

substring() ​

slice() ​

split() ​

replace() ​

includes() ​

startsWith() / endsWith() ​

padStart() / padEnd() ​

repeat() ​

charAt() ​

length ​

Number Functions ​

parseInt() ​

parseFloat() ​

toFixed() ​

toString() ​

isNaN() ​

isFinite() ​

Math Functions ​

Math.round() ​

Math.floor() ​

Math.ceil() ​

Math.abs() ​

Math.min() / Math.max() ​

Math.pow() ​

Math.sqrt() ​

Math.random() ​

Math.trunc() ​

Math.sign() ​

Array Functions ​

length ​

map() ​

filter() ​

find() ​

findIndex() ​

some() ​

every() ​

reduce() ​

sort() ​

reverse() ​

slice() ​

concat() ​

join() ​

includes() ​

indexOf() ​

flat() ​

flatMap() ​

Array.isArray() ​

Array.from() ​

Spread operator ​

Object Functions ​

Object.keys() ​

Object.values() ​

Object.entries() ​

Object.fromEntries() ​

Object.assign() ​

Spread operator ​

hasOwnProperty() ​

Date Functions ​

Date.now() ​

new Date() ​

toISOString() ​

toLocaleDateString() ​

getTime() ​

Date.parse() ​

JSON Functions ​

JSON.stringify() ​

JSON.parse() ​

Type Checking ​

typeof ​

instanceof ​

Logical Operators ​

Ternary (?😃 ​

Nullish coalescing (??) ​

Optional chaining (?.) ​

Built-in Functions

String Functions

toUpperCase()

toLowerCase()

trim()

trimStart() / trimEnd()

substring()

slice()

split()

replace()

includes()

startsWith() / endsWith()

padStart() / padEnd()

repeat()

charAt()

length

Number Functions

parseInt()

parseFloat()

toFixed()

toString()

isNaN()

isFinite()

Math Functions

Math.round()

Math.floor()

Math.ceil()

Math.abs()

Math.min() / Math.max()

Math.pow()

Math.sqrt()

Math.random()

Math.trunc()

Math.sign()

Array Functions

length

map()

filter()

find()

findIndex()

some()

every()

reduce()

sort()

reverse()

slice()

concat()

join()

includes()

indexOf()

flat()

flatMap()

Array.isArray()

Array.from()

Spread operator

Object Functions

Object.keys()

Object.values()

Object.entries()

Object.fromEntries()

Object.assign()

Spread operator

hasOwnProperty()

Date Functions

Date.now()

new Date()

toISOString()

toLocaleDateString()

getTime()

Date.parse()

JSON Functions

JSON.stringify()

JSON.parse()

Type Checking

typeof

instanceof

Logical Operators

Ternary (?😃

Nullish coalescing (??)

Optional chaining (?.)