Question 1

How to use JSON Mask with Express middleware?

Accepted Answer

Install the express-partial-response middleware via npm and add it to your app; it automatically integrates with res.json() to enable field selection via query parameters, as shown in the README server example.

Question 2

JSON Mask vs JSONPath: which one should I use?

Accepted Answer

Use JSON Mask for HTTP APIs where preserving object structure is key, as it returns filtered objects intact. JSONPath is better for complex queries that return flat arrays, but it alters the original hierarchy.

Question 3

Can JSON Mask filter arrays based on conditions?

Accepted Answer

No, JSON Mask only selects fields to keep and cannot filter array elements by values or conditions. For that, you need to pre-process the data or use a more advanced query library.

Question 4

How to handle nested objects with wildcards in JSON Mask?

Accepted Answer

Use the asterisk (*) wildcard in the mask syntax, like 'a/*/c', to select all items in a field path. This allows traversal of nested structures without specifying every level, as shown in test examples.

Question 5

Is JSON Mask suitable for browser-side data filtering?

Accepted Answer

Yes, it works in browsers with no dependencies and a small footprint (1.5KB gzipped), but it's primarily designed for server-side partial responses, so client-side use might require additional error handling.

Question 6

What are the performance implications for large objects?

Accepted Answer

It's lightweight and efficient for typical API use, but processing very large objects might have overhead since it traverses the entire structure; the README doesn't provide benchmarks, so testing is recommended for scale.

JSON Mask

What is JSON Mask?

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