course: SearchQuery : This is an object representing a course with various properties (such as course.prefix , course.number , etc.).
controller: AbortController : This allows the request to be aborted if necessary (e.g., when the user navigates away from the page before the request completes).
The function returns a Promise<GradesType> , meaning it returns a promise that resolves to an object of type GradesType after fetching and processing the data. The function makes an API request using fetchWithCache , which is likely a custom function to handle fetching data with caching support. The URL /api/grades is built dynamically by constructing query parameters from the course object: Object.keys(course) retrieves all keys from the course object.
.map() iterates over each key, creating a query string parameter in the form of key=value . The encodeURIComponent() function ensures that special characters are properly encoded in the URL.
The final URL string contains all key-value pairs joined by & , which is how query parameters are structured in URLs.
The cacheIndexNebula and expireTime are likely cache management variables that help control caching behavior for the request. The configuration object includes: signal: controller.signal : Allows the request to be aborted if needed.
method: 'GET' : Specifies that this is a GET request.
headers: { Accept: 'application/json' } : Tells the server that the client expects a JSON response.
The .then() block processes the response: First, it checks if the response.message is 'success' . If not, it throws an error with the message, which will be caught by the calling code. If response.data is null , it throws an error, indicating that no data was returned from the API.
If the response is valid, it returns an object that combines: The result of calculateGrades(response.data) , which likely computes various statistics or calculations based on the fetched grade data. This could involve calculating averages, GPAs, or other metrics. The original response.data under the grades property (this is of type GradesData , likely containing raw grade data).
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