4.3. Custom JavaScript Applications¶

4.3.1. Overview¶

You can include custom JavaScript applications (also called custom JavaScript problems or JS input problems) in a course. You add the application directly into edX Studio.

When you create a JavaScript application, Studio embeds the problem in an inline frame (HTML iframe tag) so that learners can interact with it in the LMS.

See the following sections for more information:

• Grading Options for Custom JavaScript Applications
• Use a JavaScript Application Without Grading
• Use a JavaScript Application for a Summative Assessment
• Grade the Student Response with Python
• XML for Custom JavaScript Applications

See The Custom JavaScript Display and Grading Example Template for information about the template application built in to edX Studio.

Course teams should see the following sections of the Building and Running an edX Course guide.

• Custom JavaScript Display and Grading
• Establishing a Grading Policy

The rest of this section provides more information for developers who are creating JavaScript applications for courses on the edX platform.

4.3.2. Grading Options for Custom JavaScript Applications¶

When using a JavaScript application in your course content, you have three options.

1. A JavaScript application that visually demonstrates a concept or process. The application would not require learner interaction, and learners would not be graded.
2. A JavaScript application that requires learner interaction but does not grade performance. Referred to as a formative assessment, such an application provides feedback to learners based on their interactions.
3. A JavaScript application that requires and grades learner interaction. Referred to as a summative assessment, such an application can be used to evaluate learning against a standard. To use the JavaScript application as a summative assessment and have learner performance integrated into the edX grading system, you must also use basic Python code in the component.

These options are explained through examples below.

4.3.3. Use a JavaScript Application Without Grading¶

The simplest option is to use JavaScript to show content to learners, and optionally to provide feedback as a formative assessment.

1. In edX Studio, upload an HTML file that contains the JavaScript you want to show learners.
2. Copy the Embed URL of the file.
3. Create a Custom JavaScript Display and Grading Problem. The template for the problem contains the definition for a sample JavaScript application that requires and grades learner interaction.
4. Edit the XML of the component to remove grading information and refer to the HTML file you uploaded:

<customresponse>
    <jsinput
     width="width needed to display your application"
     height="height needed to display your application"
     html_file="Embed URL of the HTML file"
     sop="false"/>
</customresponse>

For example:

<customresponse>
    <jsinput
     width="400"
     height="400"
     html_file="/static/electrol_demo.html"
     sop="false"/>
</customresponse>

4.3.4. Use a JavaScript Application for a Summative Assessment¶

To use a JavaScript Application for a summative assessment and have learner results calculated by the edX grading system, you must:

• Include these required functions in the JavaScript application.
  • getState() Function
  • setState() Function
  • getGrade() Function
• Reference functions in the problem XML.
• Grade the Student Response with Python.

<customresponse cfn="vglcfn">
    <jsinput get_statefn="JSObject.getState"
        . . . .

<customresponse cfn="vglcfn">
    <jsinput set_statefn="JSObject.setState"
        . . . .

<customresponse cfn="vglcfn">
    <jsinput gradefn="JSObject.getGrade"
        . . . .

4.3.5. Grade the Student Response with Python¶

To grade a learner’s interaction with your JavaScript application, you must write Python code in the problem. When a learner selects Submit, the Python code parses the JSON string returned by the application’s getGrade() function and determines if the learner’s submission is correct or not.

In the Python code, make sure you follow these guidelines.

• Enclose all code in a script element of type loncapa/python.
• Import json
• Define a function that is executed when the learner selects Submit, and that meets the following requirements.
  • Is placed before the customresponse element that defines the problem.
  • By default is named vglcfn
  • Has two parameters: e for the submission event, and ans, which is the JSON string returned by the JavaScript function getGrade().
  • Must return True if the learner’s submission is correct, or False if it is incorrect.

The structure of the Python code in the problem is shown in this example.

<problem>
    <script type="loncapa/python">
        import json
        def vglcfn(e, ans):
            """
            Code that parses ans and returns True or False
            """
    </script>
    <customresponse cfn="vglcfn">
    . . . .
</problem>

4.3.6. XML for Custom JavaScript Applications¶

The problem component XML that you define in Studio to provide learners with a JavaScript application has the following structure.

<problem>
    <!-- Optional script tag for summative assessments -->
    <script type="loncapa/python">
        import json
        def vglcfn(e, ans):
            """
            Code that parses ans and returns True or False
            """
    </script>
    <customresponse cfn="vglcfn">
        <jsinput
            gradefn="JSObject.getGrade"
            get_statefn="JSObject.getState"
            set_statefn="JSObject.setState"
            width="100%"
            height="360"
            html_file="/static/file-name.html"
            sop="false"/>
    </customresponse>
</problem>