Writing custom code for an e-learning course is typically done when the requirements of the course cannot be fully met by the out-of-the-box features of popular e-learning tools. Here are some scenarios where custom code might be necessary:
1. Unique Interactivity: If the course requires specific interactive elements or simulations that are not supported by standard e-learning tools, custom code might be needed to create these features.
2. Complex Assessments: Some courses might require assessments with complex logic or adaptive algorithms that are beyond the capabilities of standard quiz tools.
3. Integration with External Systems: If the course needs to integrate with external systems such as learning management systems (LMS), content management systems (CMS), or databases, custom code may be necessary to facilitate these integrations.
4. Custom User Experience: Courses that require a highly customized user experience, such as gamification elements, personalized learning paths, or advanced multimedia interactions, may benefit from custom code to achieve these features.

Advantages of writing custom code:
1. Tailored Solutions: Custom code allows for precise tailoring of the e-learning experience to meet the specific needs and objectives of the course.
2. Flexibility and Scalability: Custom code offers greater flexibility and scalability compared to out-of-the-box features, as it can be adapted and expanded as needed without being limited by the constraints of pre-built tools.
3. Innovative Features: Custom code enables the implementation of innovative features and interactive elements that can enhance engagement and learning outcomes.
4. Competitive Advantage: By creating unique and innovative e-learning experiences, organizations can gain a competitive advantage in the market.

Disadvantages of writing custom code:
1. Cost and Time: Developing custom code can be time-consuming and expensive, especially if specialized skills are required.
2. Maintenance Complexity: Custom code needs to be maintained, updated, and debugged over time, which can add complexity and cost to the long-term management of the e-learning course.
3. Compatibility Issues: Custom code may not always be compatible with all devices, browsers, or operating systems, leading to potential usability issues for learners.
4. Dependency on Developers: Organizations may become dependent on the availability and expertise of developers to maintain and update the custom code, which can pose risks if developers leave or are unavailable.

In summary, while custom code offers greater flexibility and the potential for innovative e-learning experiences, it also comes with higher costs and complexities compared to using out-of-the-box features with popular e-learning tools. The decision to write custom code should be based on a careful assessment of the specific requirements and constraints of the e-learning project.