Conditional Logic with Handlebars

This article demonstrates how to use conditional logic in Iterable templates. Find more information in the Personalizing Templates with Handlebars article.

# Display a dynamic-length array in a table with rotating background colors

The following example uses indexing and the #ifGt, #each, #ifModEq and #ifEq helpers to display a dynamic table with a user's cats' names (pulled from a cats array on the user profile).

<table cellpadding="4" cellspacing="1" width="150px">
    <thead>
        <tr>
            <th scope="col" style="background-color:#000099; color:#FFFFFF">Cat Names</th>
        </tr>
    </thead>
    <tbody>
        {{#ifGt cats.size 1}}
            {{#each cats}}
                {{#ifModEq @index 2 0}}
                    <tr style="background-color:#0099CC; color:#FFFFFF">
                        <td>
                            {{name}}
                        </td>
                    </tr>
                {{else}}
                    <tr style="background-color:#FFFFFF; color:#000000">
                        <td>
                            {{name}}
                        </td>
                    </tr>
                {{/ifModEq}}
            {{/each}}
        {{else}}
            {{#ifEq cats.size 1}}
                <tr style="background-color:#FFFFFF; color:#000000">
                    <td>
                        {{cats.[0].name}}
                    </td>
                </tr>
            {{/ifEq}}
        {{/ifGt}}
    </tbody>
</table>

# Examples

The following JSON will generate the preview below:

{
    "cats": [{
        "name": "Biscuit"
    }, {
        "name": "Lucifer"
    }, {
        "name": "Arya"
    }]
}

Another example:

{
    "cats": [{
        "name": "Biscuit"
    }]
}

# Check two optional fields for a value

This example assumes that a user profile contains a value for one of two fields: selected_city or city. To check if either of these fields is set to New York, use defaultIfEmpty:

{{#ifMatchesRegexStr (defaultIfEmpty selected_city city) "New York"}}  
    I <3 New York  
{{/ifMatchesRegexStr}}

If selected_city has a value, defaultIfEmpty returns it; otherwise, it returns the value of city. This value is then compared against the string "New York".

# Randomly display one of three values

This example outputs one of three values for a subject line, depending on the send time (in seconds). Because send time will vary based on trigger time and processing time, this approach should lead to a nearly even distribution of subject line alternatives.

{{#ifEq (math (timestamp) '%' 3) 0}}  
    Welcome to Iterable!  
{{else}}
    {{#ifEq (math (timestamp) '%' 3) 1}}  
        Greetings from Iterable!  
    {{else}}  
        Welcome, {{firstName}}!  
    {{/ifEq}}
{{/ifEq}}

# Display a fallback value if a user profile field is empty

No matter how good your data is, sometimes you'll be missing information about some of your users — which can make it tricky to send personalized messages. To avoid sending messages with blank fields, you can add fallback values that will display when a user profile field is empty:

Hi {{#ifEq firstName "firstName"}}
    {{else}}
       {{defaultIfEmpty firstName "there"}}!
    {{/ifEq}}