# Expressions

> Manipulating data with functions and expressions Fuuz Context Where this applies in Fuuz: JSONata-style expressions are used in Fuuz Data Pipelines,…

Source: https://www.fuuz.com/help/expressions
Last updated: 2025-12-26

How-To Guides · Expressions and scripting


Last updated December 26, 2025, 8:12 PM UTC

## Manipulating data with functions and expressions

## Fuuz Context

**Where this applies in Fuuz:** JSONata-style expressions are used in Fuuz Data Pipelines, Mappings, and Rule Engines to transform payloads between MES/ERP endpoints, GraphQL resolvers, and device integrations. Expressions may reference Fuuz runtime variables (e.g., `$env`, `$tenant`) and step context values exposed by the pipeline.

- **Mappings:** Use concatenation (`&`) and numeric operators to build outbound fields from inbound JSON and Fuuz step outputs.
- **Rules:** Predicates using comparison/boolean operators drive routing (e.g., reject, retry, branch) within a pipeline.
- **Best practice:** Prefer explicit casting (`$string()`, `$number()`) when mixing types returned by connectors.

## String expressions

Path expressions that point to a string value will return that value.

String literals can also be created by enclosing the

sequence of characters in quotes. Either double quotes `"` or single quotes `'` can be used, provided the same quote type is

used for the start and end of the string literal. Single quote characters may be included within a double quoted string and

_vice versa_ without escaping. Characters within the string literal may be escaped using the same format

as [JSON strings](https://tools.ietf.org/html/rfc7159#section-7).

Strings can be combined using the concatenation operator `&`. This is an infix operator and will join the two strings

returned by the expressions either side of it. This is the only operator that will attempt to typecast its operands to

the expected (string) type.

**Examples**

- Concatenate `FirstName` followed by space followed by `Surname`

<div class="jsonata-ex">

<div>FirstName & ' ' & Surname</div>

<div>"Fred Smith"</div>

</div>

- Concatenates the `Street` and `City` from the `Address` object with a comma separator. Note the use of [parentheses](composition.md#parenthesized-expressions-and-blocks)

<div class="jsonata-ex">

<div>Address.(Street & ', ' & City)</div>

<div>"Hursley Park, Winchester"</div>

</div>

- Casts the operands to strings, if necessary

<div class="jsonata-ex">

<div>5&0&true</div>

<div>"50true"</div>

</div>

## Numeric expressions

Path expressions that point to a number value will return that value.

Numeric literals can also be created using the same syntax as [JSON numbers](https://tools.ietf.org/html/rfc7159#section-6).

Numbers can be combined using the usual mathematical operators to produce a resulting number. Supported operators:

- `+` addition
- `-` subtraction
- `*` multiplication
- `/` division
- `%` remainder (modulo)

**Examples**

Consider the following JSON document:

```

{
  "Numbers": [1, 2.4, 3.5, 10, 20.9, 30]
}

```
| Expression | Output | Comments

| ---------- | ------ |----|

| `Numbers[0] + Numbers[1]` | 3.4 |Adding 2 prices|

| `Numbers[0] - Numbers[4]` | -19.9 | Subtraction |

| `Numbers[0] * Numbers[5]` | 30 |Multiplying price by quantity|

| `Numbers[0] / Numbers[4]` | 0.04784688995215 |Division|

| `Numbers[2] % Numbers[5]` | 3.5 |Modulo operator|

## Comparison expressions

Often used in predicates, for comparison of two values. Returns Boolean `true` or `false`. Supported operators:

- `=` equals
- `!=` not equals
- `<` less than
- `<=` less than or equal
- `>` greater than
- `>=` greater than or equal
- `in` value is contained in an array

**Examples**

| Expression | Output | Comments

| ---------- | ------ |----|

| `Numbers[0] = Numbers[5]` | false |Equality |

| `Numbers[0] != Numbers[4]` | true | Inequality |

| `Numbers[1] < Numbers[5]` | true |Less than|

| `Numbers[1] <= Numbers[5]` | true |Less than or equal|

| `Numbers[2] > Numbers[4]` | false |Greater than|

| `Numbers[2] >= Numbers[4]` | false |Greater than or equal|

| `"01962 001234" in Phone.number` | true | Value is contained in|

## Boolean expressions

Used to combine Boolean results, often to support more sophisticated predicate expressions. Supported operators:

- `and`
- `or`

Note that `not` is supported as a function, not an operator.

**Examples**

| Expression | Output | Comments

| ---------- | ------ |----|

| `(Numbers[2] != 0) and (Numbers[5] != Numbers[1])` | true |`and` operator |

| `(Numbers[2] != 0) or (Numbers[5] = Numbers[1])` | true | `or` operator |

### Need more help?

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[Ask the community](https://www.fuuz.com/community) [Open a ticket](https://support.fuuz.com/portal/en/newticket)

On this page

[Manipulating data with functions and expressions](#manipulating-data-with-functions-and-expressions)

[Fuuz Context](#fuuz-context)

[String expressions](#string-expressions)

[Numeric expressions](#numeric-expressions)

[Comparison expressions](#comparison-expressions)

[Boolean expressions](#boolean-expressions)