Expressions

Expressions are a powerful data processing tool in Atomemo that allow you to dynamically access, transform, and manipulate data in your workflows.

What are Expressions?

Expressions are a special syntax for accessing and manipulating workflow data. With expressions, you can:

• Access node data - Reference output data from any node
• Transform data - Use built-in methods to process arrays, strings, numbers, etc.
• Dynamic calculations - Perform mathematical operations and logical judgments
• Combine data - Merge multiple data sources into new outputs

Basic Syntax

Accessing Node Data

In Atomemo, expressions must explicitly specify the node name:

// Access node outputs
$('Chat Trigger').message
$('HTTP Request').body.userId
$('Entity Recognition').productName

// Use expressions in strings
`User ${$('Chat Trigger').userId} order status: ${$('HTTP Request').body.status}`

Important: Expression syntax always requires specifying the node name. Shortcuts like $json.field are not supported.

Expression Contexts

Expressions can be used in:

• Node parameters - Any input field that supports expressions
• Conditional logic - Condition expressions in IF nodes
• Code nodes - Access data in JavaScript/Python code
• HTTP requests - Dynamically build URLs, headers, body

Data Types & Methods

The Atomemo expression engine provides rich built-in methods for different data types:

Arrays

Methods for processing array data, including filtering, transformation, aggregation, etc.

// Examples
$('HTTP Request').body.items.first()
$('HTTP Request').body.prices.average()
$('HTTP Request').body.users.pluck('name')

Booleans

Boolean conversion and manipulation methods.

// Example
$('HTTP Request').body.isActive.toInt()

Dates

Date and time processing methods, including formatting, calculations, comparisons, etc.

// Examples
$('Chat Trigger').timestamp.format('yyyy-MM-dd')
$('HTTP Request').body.createdAt.plus(7, 'day')

Numbers

Number operations and conversion methods.

// Examples
$('HTTP Request').body.price.round(2)
$('HTTP Request').body.count.isEven()

Objects

Object manipulation methods, including merging, filtering, transforming, etc.

// Examples
$('HTTP Request').body.user.hasField('email')
$('HTTP Request').body.config.merge({ newKey: 'value' })

Strings

String processing methods, including formatting, parsing, validation, etc.

// Examples
$('Chat Trigger').message.toUpperCase()
$('HTTP Request').body.email.isEmail()
$('HTTP Request').body.url.extractDomain()

Common Use Cases

1. Accessing Nested Data

// Access deeply nested object properties
$('HTTP Request').body.user.profile.address.city

// Access array elements
$('HTTP Request').body.items[0].name
$('HTTP Request').body.items[1].price

2. Data Transformation

// Convert string to number
$('Chat Trigger').message.toInt()

// Format date
$('HTTP Request').body.createdAt.format('yyyy-MM-dd HH:mm:ss')

// Convert object to JSON string
$('HTTP Request').body.toJsonString()

3. Conditional Logic

// Check if value exists
$('HTTP Request').body.email.isNotEmpty()

// Check number range
$('HTTP Request').body.age > 18

// Check date range
$('HTTP Request').body.createdAt.isInLast(7, 'day')

4. Array Operations

// Get array length
$('HTTP Request').body.items.length

// Extract specific field
$('HTTP Request').body.users.pluck('email')

// Filter array
$('HTTP Request').body.items.filter(item => item.price > 100)

// Array aggregation
$('HTTP Request').body.prices.sum()
$('HTTP Request').body.scores.average()

5. String Concatenation

// Use template strings
`Hello, ${$('HTTP Request').body.user.name}!`

// Concatenate multiple values
`Order ${$('HTTP Request').body.orderId} status: ${$('HTTP Request').body.status}`

Best Practices

1. Use Clear Node Names

// Good - Clear node names
$('Get User Info').body.name
$('Query Orders').body.items

// Bad - Unclear node names
$('HTTP Request').body.name
$('HTTP Request 1').body.items

2. Handle Potentially Missing Data

// Use optional chaining
$('HTTP Request').body?.user?.email

// Provide default values
$('HTTP Request').body.user.name || 'Anonymous'

// Check existence
$('HTTP Request').body.user.hasField('email')

3. Avoid Overly Complex Expressions

// Good - Process in steps
// Handle complex logic in Code node, then reference results
$('Process Data').result

// Bad - Too complex
$('HTTP Request').body.items.filter(item => item.price > 100).pluck('name').join(', ')

4. Use Type Conversion

// Ensure correct data types
$('Chat Trigger').message.toInt()
$('HTTP Request').body.isActive.toBoolean()
$('HTTP Request').body.timestamp.toDate()

5. Test Expressions

When developing workflows:

1. Use console.log() in Code nodes to test expressions
2. Check output data after node execution
3. Use expression editor's preview feature to verify results

Error Handling

Common Errors

1. Node doesn't exist

   // Error: Referencing non-existent node
   $('Nonexistent Node').data
   
   // Solution: Ensure node name is correct
   $('HTTP Request').data

2. Property doesn't exist

   // Error: Accessing non-existent property
   $('HTTP Request').body.nonexistentField
   
   // Solution: Use optional chaining or check
   $('HTTP Request').body?.nonexistentField
   $('HTTP Request').body.hasField('nonexistentField')

3. Type error

   // Error: Calling number method on string
   $('Chat Trigger').message.round()
   
   // Solution: Convert type first
   $('Chat Trigger').message.toInt().round()

Debugging Tips

1. Use Code Node for Debugging

// Print expression results in Code node
console.log('User data:', $('HTTP Request').body.user);
console.log('Item count:', $('HTTP Request').body.items.length);
return $('HTTP Request').body;

2. Step-by-Step Validation

Break complex expressions into multiple steps, validating results at each step:

HTTP Request Node
  → Code Node (Validate and transform data)
  → IF Node (Conditional logic)
  → Answer Node (Return result)

3. Use Expression Editor

The expression editor provides:

• Syntax highlighting
• Auto-completion
• Live preview
• Error hints

Performance Considerations

1. Avoid Repeated Calculations

// Bad - Repeated calculations
`${$('HTTP Request').body.items.length} items, total: ${$('HTTP Request').body.items.sum()}`

// Good - Calculate once in Code node, then reference
$('Calculate Stats').summary

2. Limit Array Size

Be mindful of performance when processing large arrays:

// For large arrays, consider filtering first
$('HTTP Request').body.items
  .filter(item => item.active)
  .slice(0, 100)
  .pluck('name')

Next Steps

• Array Methods Reference
• String Methods Reference
• Date Methods Reference
• Object Methods Reference
• Number Methods Reference
• Boolean Methods Reference

Related Resources

• Code Node - Use expressions in code
• IF Node - Conditional expressions
• HTTP Request Node - Use expressions in API calls