⚡ Template Expressions

Loopstack uses two distinct expression syntaxes for dynamic content rendering and data access throughout your automation configurations.

Expression Syntax Overview

Template Expressions ({{ }}) - Used for rendering dynamic content within text, typically in tool arguments, message content, and document templates:


tools:
  - name: email_sender_tool
    execute:
      - handler: EmailHandler
        arguments:
          subject: "Welcome {{user.name}}!"                    # Template expression
          body: |
            Hello {{user.name}},
 
            {{#if user.isPremium}}
              Thank you for being a premium member!
            {{else}}
              Consider upgrading to premium for more features.
            {{/if}}
 
            Best regards,
            The Team

Property Accessors (${ }) - Used for accessing variables and context data in YAML configuration values:


tools:
  - name: data_processor_tool
    execute:
      - handler: DataProcessingHandler
        arguments:
          input_data: ${ EXTRACTED_DATA }                      # Property accessor
          user_id: ${ context.variables.USER_ID }             # Context access
          processing_mode: ${ options.mode }                  # Template options
          api_endpoint: ${ context.custom.apiUrl }            # Custom context

Both syntaxes can access the same underlying data, but serve different purposes:

Template expressions render dynamic text content with conditional logic and formatting (always outputs strings)
Property accessors inject raw data values into configuration parameters while preserving the original data type (string, object, array, boolean, etc.)

Loopstack uses Handlebars for rendering dynamic content. This is a comprehensive guide to available Handlebars syntax and helpers for template rendering.

Template Expressions {{ }}

Template expressions can utilize a range of different Handlebars features and helpers:

Handlebars Syntax

Simple variable

{{TEST_OBJECT.name}}

Nested property

{{TEST_OBJECT.profile.email}}

Array access

{{TEST_OBJECT.items.[0]}}

Default Helpers

if

{{#if TEST_OBJECT.isActive}}Welcome back!{{/if}}

if/else

{{#if TEST_OBJECT.isAdmin}}Admin Panel{{else}}User Panel{{/if}}

unless

{{#unless TEST_OBJECT.isBlocked}}Access granted{{/unless}}

each

{{#each TEST_OBJECT.users}}<li>{{this.name}}</li>{{/each}}

each with else

{{#each TEST_OBJECT.items}}{{this}}{{else}}No items{{/each}}

Comparison and Logic Helpers

eq

strict equality

{{#if (eq TEST_OBJECT.role "admin")}}Admin{{/if}}

ne

strict inequality

{{#if (ne TEST_OBJECT.status "inactive")}}active{{/if}}

looseEq

loose equality

{{#if (looseEq TEST_OBJECT.count "5")}}Five{{/if}}

looseNe

loose inequality

{{#if (looseNe TEST_OBJECT.value null)}}Has value{{/if}}

gt

greater than

{{#if (gt TEST_OBJECT.age 18)}}Adult{{/if}}

gte

greater than or equal

{{#if (gte TEST_OBJECT.score 90)}}Perfect!{{/if}}

lt

less than

{{#if (lt TEST_OBJECT.cold 32)}}Freezing{{/if}}

lte

less than or equal

{{#if (lte TEST_OBJECT.age 30)}}Young adult{{/if}}

and

{{#if (and TEST_OBJECT.isActive TEST_OBJECT.isVerified)}}Verified user{{/if}}

or

{{#if (or TEST_OBJECT.isPremium TEST_OBJECT.isTrial)}}Premium features{{/if}}

not

{{#if (not TEST_OBJECT.isBlocked)}}Welcome{{/if}}

contains

{{#if (contains TEST_OBJECT.email "@company.com")}}Employee{{/if}}

startsWith

{{#if (startsWith TEST_OBJECT.doctor "Dr.")}}Doctor{{/if}}

endsWith

{{#if (endsWith TEST_OBJECT.file.name ".pdf")}}PDF file{{/if}}

regexTest

{{#if (regexTest TEST_OBJECT.phone "^\\+1")}}US number{{/if}}

regexTest with flags {{#if (regexTest TEST_OBJECT.email "^[A-Z]+@" "i")}}Valid email{{/if}}

in

in (array)

{{#if (in TEST_OBJECT.role TEST_OBJECT.validRoles)}}Valid role{{/if}}

in (object) {{#if (in "email" TEST_OBJECT)}}Has email{{/if}}

length

Total: {{length TEST_OBJECT.items}}

isEmpty

{{#if (isEmpty TEST_OBJECT.empty)}}No tags{{/if}}

typeOf

Type: {{typeOf TEST_OBJECT.value}}

isNull

{{#if (isNull TEST_OBJECT.deletedAt)}}Active{{/if}}

isUndefined

{{#if (isUndefined TEST_OBJECT.tempData)}}No temp data{{/if}}

isNumber

{{#if (isNumber TEST_OBJECT.age)}}Age: {{TEST_OBJECT.age}}{{/if}}

isString

{{#if (isString TEST_OBJECT.bio)}}{{TEST_OBJECT.bio}}{{/if}}

isBoolean

{{#if (isBoolean TEST_OBJECT.flag)}}Boolean value{{/if}}

isArray

{{#if (isArray TEST_OBJECT.items)}}List of items{{/if}}

isObject

{{#if (isObject TEST_OBJECT)}}User object{{/if}}

Mathematical Operations

add

Total: ${{add TEST_OBJECT.price TEST_OBJECT.tax TEST_OBJECT.shipping}}

subtract

Discount: ${{subtract TEST_OBJECT.original TEST_OBJECT.sale}}

multiply

Tax: ${{multiply TEST_OBJECT.price 0.08}}

divide

Average: {{divide TEST_OBJECT.total TEST_OBJECT.count}}

modulo

Remainder: {{modulo 17 5}}

Utility Helpers

default

Name: {{default TEST_OBJECT.displayName TEST_OBJECT.username}}

Date and Time

Current Date

currentDate

Today: {{currentDate}}

currentDate with format {{currentDate "yyyy-MM-dd"}}

currentDate with time {{currentDate "yyyy-MM-dd h:mm"}}

Date Formatting

formatDate

Created: {{formatDate TEST_OBJECT.createdAt}}

formatDate with format {{formatDate TEST_OBJECT.event.date "yyyy-MM-dd"}}

Time Ago

timeAgo

Last seen: {{timeAgo TEST_OBJECT.lastLoginAt}}

timeAgo for comments Posted {{timeAgo TEST_OBJECT.comment.createdAt}}

timeAgo for events Event ended {{timeAgo TEST_OBJECT.event.endDate}}