Using Handlebars.js to dynamically set classes based on key/value pairs in JSON data

Question

Using Handlebars.js to dynamically set classes based on key/value pairs in JSON data

Today, I delved into the world of Handlebars.js and sought a straightforward approach. Let’s set the stage: We are unable to control how the JSON data was generated (thus, server-side solutions are out). The JSON will consist of one or more records, each containing a Message_Type name/value pair with values that hold relevance for certain functions involving CSS classes in presentation.

For example: message types may include basic, ad, notification, warning, critical, etc., with corresponding CSS classes. For instance, a critical message type might be styled with classes such as .msg_box and .critical_msg.

My question is this: How should I tackle this issue without altering the original source? Option 1: Process the JSON data before passing it to Handlebars, adding new name/value pairs for each record that specify the required classes. Option 2: Implement a solution within Handlebars itself—which remains unclear to me.

javascript css json handlebars.js

Answer 1

Answer №1

I think the best way to handle this with Handlebars is to parse your JSON data and dynamically assign the necessary class names before passing it to the Handlebars template. While there are ways to manipulate Handlebars to include logical operators, such as discussed in this Stack Overflow thread, it's generally not recommended.

var messageMapping = {
  basic: 'msg_box',
  ad: 'msg_box',
  notification: 'msg_box',
  warning: 'critical_msg',
  critical: 'critical_msg'
};

// Your JSON data from the server
var yourJSON = '[{"message_type":"basic", "value":"test"},{"message_type":"warning", "value":"test"}]';

var data = JSON.parse(yourJSON),
    i = 0,
    l = data.length;

// Assign the class names
for(; i < l; i++){
  data[i].msgClass = messageMapping[data[i].message_type];  
}

// Render the template
var source   = $('#template').html();
var template = Handlebars.compile(source);

$('body').append(template({messages:data}));

.critical_msg{
  background-color:red;  
}

.msg_box{
  background-color:green;  
}

<script src="//cdnjs.cloudflare.com/ajax/libs/handlebars.js/2.0.0/handlebars.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script id='template' type='template/text'>
{{#each messages}}
  <div class="{{msgClass}}">{{value}}</div>
{{/each}}
</script>

Answer 2

I think the best way to handle this with Handlebars is to parse your JSON data and dynamically assign the necessary class names before passing it to the Handlebars template. While there are ways to manipulate Handlebars to include logical operators, such as discussed in this Stack Overflow thread, it's generally not recommended.

var messageMapping = {
  basic: 'msg_box',
  ad: 'msg_box',
  notification: 'msg_box',
  warning: 'critical_msg',
  critical: 'critical_msg'
};

// Your JSON data from the server
var yourJSON = '[{"message_type":"basic", "value":"test"},{"message_type":"warning", "value":"test"}]';

var data = JSON.parse(yourJSON),
    i = 0,
    l = data.length;

// Assign the class names
for(; i < l; i++){
  data[i].msgClass = messageMapping[data[i].message_type];  
}

// Render the template
var source   = $('#template').html();
var template = Handlebars.compile(source);

$('body').append(template({messages:data}));

.critical_msg{
  background-color:red;  
}

.msg_box{
  background-color:green;  
}

<script src="//cdnjs.cloudflare.com/ajax/libs/handlebars.js/2.0.0/handlebars.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script id='template' type='template/text'>
{{#each messages}}
  <div class="{{msgClass}}">{{value}}</div>
{{/each}}
</script>

Answer 3

Answer №2

Handlebars was intentionally created to operate without heavy logic, meaning it lacks built-in features for making decisions based on data other than a simple if statement regarding the existence of certain data. It does not intrinsically support determining what HTML class to apply based on the value of a data element.

Given this limitation, there are several approaches you can take:

If the templates are used on the client-side, preprocess the JSON data before sending it to the template in a format that doesn't require complex logic.
Create custom helper functions that can receive data and make decisions based on it, then communicate those decisions back to the template.
Integrate helper methods that extend Handlebars' capabilities by adding more advanced logic features (there are existing pre-built ones available).
Consider transitioning to a different template engine that offers more extensive built-in logic capabilities.

Answer 4

Handlebars was intentionally created to operate without heavy logic, meaning it lacks built-in features for making decisions based on data other than a simple if statement regarding the existence of certain data. It does not intrinsically support determining what HTML class to apply based on the value of a data element.

Given this limitation, there are several approaches you can take:

If the templates are used on the client-side, preprocess the JSON data before sending it to the template in a format that doesn't require complex logic.
Create custom helper functions that can receive data and make decisions based on it, then communicate those decisions back to the template.
Integrate helper methods that extend Handlebars' capabilities by adding more advanced logic features (there are existing pre-built ones available).
Consider transitioning to a different template engine that offers more extensive built-in logic capabilities.

Using Handlebars.js to dynamically set classes based on key/value pairs in JSON data

Answer №1

Answer №2

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