Parse the query parameters

Oct 13, 2025 by pynkocean.com 126 views

As a user, it is essential to be able to query an attribute given a range, so that you can quickly identify item boundaries in your cart. This feature will enable you to filter items based on specific criteria, making it easier to manage your shopping cart.

Details and Assumptions

To implement this feature, the user will pass in their user ID and a range for each attribute they want to query. The base GET /shopcarts/{user_id} route will be updated to accommodate this new functionality. No new route will be created, and the existing route will be modified to handle the query parameters.

Acceptance Criteria

The following scenarios outline the expected behavior of the system:

Given our REST API
When a user sends in a query for a price range in the form GET /shopcarts/123/range_price=50,100
Then they should get the items in user 123's shopcart within the price range.

Given our REST API
When a user sends in a query for a quantity range in the form GET /shopcarts/123/range_qty=50,100
Then they should get the items in user 123's shopcart within the quantity range.

Given our REST API
When a user sends in a query for a quantity range and price range in the form GET /shopcarts/123/range_qty=50,100&range_price=50,100
Then they should get the items in user 123's shopcart within the quantity range and price range.

Given our REST API
When a user sends in a query for a range but only provides 1 value (e.g GET /shopcarts/123/range_qty=50)
Then they should get an error since we cannot assume whether it is the minimum or maximum.

Implementation

To implement this feature, we will update the existing GET /shopcarts/{user_id} route to handle the query parameters. We will use the following approach:

Parse the query parameters: We will use a library like query-string to parse the query parameters and extract the range values.
Validate the range values: We will validate the range values to ensure that they are valid numbers and that the minimum value is less than or equal to the maximum value.
Filter the items: We will use the validated range values to filter the items in the user's shopcart. We will use a library like lodash to perform the filtering.
Return the filtered items: We will return the filtered items in the response.

Example Use Cases

Here are some example use cases for this feature:

Querying by price range: A user wants to query their shopcart for items with a price between $50 and $100. They send a GET request to /shopcarts/123/range_price=50,100. The system returns the items in the user's shopcart that meet the price range criteria.
Querying by quantity range: A user wants to query their shopcart for items with a quantity between 50 and 100. They send a GET request to /shopcarts/123/range_qty=50,100. The system returns the items in the user's shopcart that meet the quantity range criteria.
Querying by multiple ranges: A user wants to query their shopcart for items with a price between $50 and $100 and a quantity between 50 and 100. They send a GET request to /shopcarts/123/range_qty=50,100&range_price=50,100. The system returns the items in the user's shopcart that meet both range criteria.

Error Handling

If a user sends a query with only one value, the system will return an error. This is because we cannot assume whether the single value is the minimum or maximum value of the range.

Conclusion

In conclusion, this feature will enable users to query their shopcart by attribute range, making it easier to manage their shopping cart. We will update the existing GET /shopcarts/{user_id} route to handle the query parameters and return the filtered items in the response. We will also handle errors that may occur when a user sends a query with only one value.

Future Development

In the future, we can enhance this feature by adding more advanced filtering capabilities, such as filtering by multiple attributes or using more complex range criteria. We can also add support for filtering by other attributes, such as item name or category.

API Documentation

Here is an example of how the API documentation for this feature might look:

GET /shopcarts/{user_id}

Query Parameters:
- range_price: The price range to filter by (e.g. 50,100)
- range_qty: The quantity range to filter by (e.g. 50,100)
Response:
- A list of items in the user's shopcart that meet the filter criteria

Code Implementation

Here is an example of how the code implementation for this feature might look:

const express = require('express');
const querystring = require('query-string');
const _ = require('lodash');

const app = express();

app.get('/shopcarts/:user_id', (req, res) => {
  const userId = req.params.user_id;
  const query = querystring.parse(req.query);
  const rangePrice = query.range_price;
  const rangeQty = query.range_qty;

  if (!rangePrice || !rangeQty) {
    return res.status(400).send({ error: 'Invalid range values' });
  }

  const items = getItemsForUser(userId);
  const filteredItems = _.filter(items, (item) => {
    const price = item.price;
    const quantity = item.quantity;

    return (price >= rangePrice[0] && price <= rangePrice[1]) &&
           (quantity >= rangeQty[0] && quantity <= rangeQty[1]);
  });

  res.send(filteredItems);
});

function getItemsForUser(userId) {
  // This function would retrieve the items for the user from the database
  // For the purpose of this example, we will assume that the items are already in memory
  const items = [
    { id: 1, price: 50, quantity: 50 },
    { id: 2, price: 75, quantity: 75 },
    { id: 3, price: 100, quantity: 100 },
  ];

  return items;
}

This code implementation uses the express framework to handle the GET request and the query-string library to parse the query parameters. It then uses the lodash library to filter the items based on the range values. Finally, it returns the filtered items in the response.
Query Items for a User Given a Range of an Attribute: Q&A

Q: What is the purpose of this feature? A: The purpose of this feature is to enable users to query their shopcart by attribute range, making it easier to manage their shopping cart.

Q: How does this feature work? A: This feature works by updating the existing GET /shopcarts/{user_id} route to handle the query parameters. The user passes in their user ID and a range for each attribute they want to query. The system then filters the items in the user's shopcart based on the range values and returns the filtered items in the response.

Q: What are the query parameters for this feature? A: The query parameters for this feature are:

range_price: The price range to filter by (e.g. 50,100)
range_qty: The quantity range to filter by (e.g. 50,100)

Q: What is the format of the query parameters? A: The query parameters are in the format of key=value where key is the attribute name and value is the range value. For example, range_price=50,100 or range_qty=50,100.

Q: What happens if a user sends a query with only one value? A: If a user sends a query with only one value, the system will return an error. This is because we cannot assume whether the single value is the minimum or maximum value of the range.

Q: Can I filter by multiple attributes? A: Yes, you can filter by multiple attributes. For example, you can send a query with both range_price and range_qty parameters. The system will filter the items based on both range values.

Q: Can I filter by other attributes? A: Yes, you can filter by other attributes. For example, you can add a range_name parameter to filter by item name. The system will filter the items based on the range value for the specified attribute.

Q: How do I implement this feature? A: To implement this feature, you will need to update the existing GET /shopcarts/{user_id} route to handle the query parameters. You will also need to add logic to filter the items based on the range values.

Q: What are the benefits of this feature? A: The benefits of this feature include:

Improved user experience: Users can quickly and easily filter their shopcart by attribute range.
Increased efficiency: Users can quickly identify the items in their shopcart that meet their filter criteria.
Enhanced functionality: Users can filter by multiple attributes and use more complex range criteria.

Q: Are there any limitations to this feature? A: Yes, there are limitations to this feature. For example:

The system will return an error if a user sends a query with only one value.
The system will only filter by the attributes specified in the query parameters.
The system will only return items that meet the filter criteria.

Q: Can I customize this feature? A: Yes, you can customize this feature to meet your specific needs. For example, you can add additional query parameters or modify the filtering logic to suit your requirements.

Q: How do I test this feature? A: To test this feature, you will need to send a GET request to the updated GET /shopcarts/{user_id} route with the query parameters. You can use a tool like Postman or cURL to send the request. You should then verify that the system returns the filtered items in the response.