Handlebars in five minutes

Handlebars is the template engine behind Asgard's Template mode, letting you produce dynamic text with concise syntax.

The basics

Handlebars inserts dynamic content with braces, and there are two forms:

Double braces versus triple braces

Double braces {{}} — HTML escaped

Hello {{name}}! Your order number is {{orderNumber}}

Triple braces {{{}}} — not escaped

Hello {{{name}}}! Your order number is {{{orderNumber}}}

Syntax	Purpose	HTML escaping	Example
{{}}	Ordinary text output	✅ escaped	{{content}} → <script>
{{{}}}	Raw output	❌ not escaped	{{{content}}} → <script>

What to use in Asgard

In Asgard, use triple braces {{{}}} in most cases, because:

• It avoids unintended conversion: special characters are not mangled (< becoming <, say)
• It keeps data intact: the variable's content comes out as it went in

Hello {{{name}}}! Your order number is {{{orderNumber}}}

Output:

Hello Alice! Your order number is ORD20240115001

📖 Learning the syntax properly
The full Handlebars syntax is in the official documentation

Core syntax

Inserting a variable

Hello {{{user.name}}}! Your membership tier is {{{user.level}}}

Conditionals

{{#if hasNewOrders}}
  You have
  {{{newOrderCount}}}
  new orders
{{else}}
  No new orders right now
{{/if}}

Loops

• Products:
{{#each products}}
  {{{@index}}}.
  {{{name}}}
  - NT$
  {{{price}}}
{{/each}}

Asgard's built-in helpers

Asgard provides eight helpers:

{{{history 0 -1}}}
<!-- conversation history -->

{{{historySize}}}
<!-- how many messages -->

{{{toJson user}}}
<!-- convert to JSON -->

{{{urlEncode searchKeyword}}}
<!-- URL encode -->

{{{xpathExtract xmlData '/root/item'}}}
<!-- XML lookup -->

{{{vecToStr vector '[' ']' ','}}}
<!-- vector to string -->

{{{isoNow 'Asia/Taipei'}}}
<!-- the time now -->

{{{isoToday 'Asia/Taipei'}}}
<!-- today's date -->

Worked examples

A basic message template

Hello
{{{user.name}}}! 
System status: 
• Messages: {{{historySize}}}
• The time now: {{{isoNow 'Asia/Taipei'}}}

{{#if hasUpdates}}
  Recent messages:
  {{{history -3 -1}}}
{{/if}}

A button template

{
  "type": "BUTTON",
  "title": "{{{user.name}}}'s details",
  "text": "Membership details:\n{{{toJson user}}}",
  "buttons": [
    {
      "label": "See the history",
      "action": {
        "type": "MESSAGE",
        "text": "Show the conversation history"
      }
    }
  ]
}

An API query

• Search: {{{urlEncode query}}}
• Queried at: {{{isoNow 'Asia/Taipei'}}}

{{#if xmlResponse}}
• Results:
  {{{xpathExtract xmlResponse '//item/title'}}}
{{/if}}

Choosing between Template and Expression

Situation	Use	Why
Text templates	Template	Concise syntax
Complex computation	Expression	The whole of JavaScript
Conditionals	Template	Built in
Arithmetic	Expression	More flexible

Quick checklist

✅ Insert a variable: {{{variable}}}
✅ Conditional: {{#if condition}}
✅ Loop: {{#each array}}
✅ Asgard helpers: eight of them
✅ Object properties: {{{user.name}}} for nested access

Going further

• The Handlebars guide
• The full list of Asgard's built-in helpers

Standard Handlebars syntax plus Asgard's helpers is enough to build capable dynamic message templates.