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Compute Field (Free Online Tool)

Create derived values or fields from formulas, expressions, and simple conditionals

Paste your JSON → Get results instantly (no signup)

⚡ Instant resultsNo signupRuns in your browser
Try examples:

→ Create a derived field by concatenating existing fields.

[
{
"firstName": "Alice",
"lastName": "Smith"
},
{
"firstName": "Bob",
"lastName": "Jones"
}
]
Output✓
1[
2  {
3    "firstName": "Alice",
4    "lastName": "Smith",
5    "fullName": "Alice Smith"
6  },
7  {
8    "firstName": "Bob",
9    "lastName": "Jones",
10    "fullName": "Bob Jones"
11  }
12]

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Uses example data. For edited input, copy from the playground.

Read integration guide

Works with:

  • API responses
  • Nested JSON
  • Arrays & objects

Example: input → output

Related tools

Advanced usage (optional)

Compute Field

v1.0.0
Convert
objectarray

Description

Compute Field

Create derived fields from expressions — concatenation, math calculations, and conditional logic. Adds a new computed field to each object without modifying existing data.

How It Works

The expression uses {{fieldName}} template syntax to reference fields from each object. The utility evaluates the expression and writes the result to a new field.

String Concatenation

When the expression contains text outside of {{}} references, the result is a string with values interpolated.

"{{firstName}} {{lastName}}" → "Alice Smith"

Math Calculations

When the expression is purely numeric operations on field references, the result is evaluated as a math expression.

"{{price}} * {{quantity}}" → 50

Conditional Logic

Use ternary operators for conditional values.

"{{age}} >= 18 ? \"adult\" : \"minor\"" → "adult"

Configuration

FieldTypeDefaultDescription
Target Pathspath-picker[]Scope to specific objects (empty = apply to root / all items)
Output Field Namestring"computed"Key name for the computed result
Expressionstring""Template with {{fieldName}} references

Expression Syntax

Field References

{{fieldName}}         — top-level field
{{address.city}}      — nested field (dot notation)

String Templates

"{{firstName}} {{lastName}}"              → "Alice Smith"
"Hello, {{name}}!"                        → "Hello, Alice!"
"{{city}}, {{state}} {{zip}}"             → "NYC, NY 10001"

Math Operations

"{{price}} * {{quantity}}"                → 50
"{{total}} - {{discount}}"               → 85
"({{width}} + {{height}}) * 2"           → 30

Conditional Expressions

"{{age}} >= 18 ? \"adult\" : \"minor\""   → "adult"
"{{score}} > 90 ? \"A\" : \"B\""          → "A"
"{{stock}} > 0 ? \"available\" : \"out\"" → "available"

Use Cases

Data Enrichment

  • Full names: Combine first and last name fields
  • Display addresses: Concatenate city, state, zip into a single line
  • Labels: Generate display labels from multiple fields

Calculations

  • Line totals: Multiply price by quantity
  • Discounts: Calculate discounted prices
  • Percentages: Compute ratios between fields

Classification

  • Age groups: Categorize by age ranges
  • Grade letters: Map numeric scores to letter grades
  • Status flags: Derive status from threshold values

Configuration

NameTypeDefaultDescription
Target Pathspath-picker[]Scope to specific objects (empty = apply to root / all items)
Output Field NamestringcomputedKey name for the computed result
ExpressionexpressionTemplate with {{fieldName}} refs. Refs resolve at the FIRST object in the walk where they're found — that's also where the computed field lands. String: "{{firstName}} {{lastName}}" Math: "{{price}} * {{quantity}}" Conditional: "{{age}} >= 18 ? \"adult\" : \"minor\"" Nested ref: "{{payments.0.amount}}" — lifts a value from a nested array/object up to its parent record (numeric segments index arrays).

Examples

AI Prompt
Create a derived field by concatenating existing fields.
[
{
"firstName": "Alice",
"lastName": "Smith"
},
{
"firstName": "Bob",
"lastName": "Jones"
}
]
Output✓
1[
2  {
3    "firstName": "Alice",
4    "lastName": "Smith",
5    "fullName": "Alice Smith"
6  },
7  {
8    "firstName": "Bob",
9    "lastName": "Jones",
10    "fullName": "Bob Jones"
11  }
12]
Config
Target Paths
all
Output Field Name
fullName
Expression
{{firstName}} {{lastName}}

API Usage

POST /api/v1/utilities/convert.compute
Example:
curl -X POST https://your-domain.com/api/v1/utilities/convert.compute \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"inputs":{"primary":[{"firstName":"Alice","lastName":"Smith"},{"firstName":"Bob","lastName":"Jones"}]},"config":{"targetPaths":[],"targetField":"fullName","expression":"{{firstName}} {{lastName}}"}}'
Response
1[
2  {
3    "firstName": "Alice",
4    "lastName": "Smith",
5    "fullName": "Alice Smith"
6  },
7  {
8    "firstName": "Bob",
9    "lastName": "Jones",
10    "fullName": "Bob Jones"
11  }
12]