JavaScript API Deprecation in the Wild: A First Assessment (SANER 2020)

Building an application using third-party libraries is a common practice in software development. As any other software system, code libraries and their APIs evolve over time. In order to help version migration and ensure backward compatibility, a recommended practice during development is to deprecate API. Although studies have been conducted to investigate deprecation in some programming languages, such as Java and C#, there are no detailed studies on API deprecation in the JavaScript ecosystem. This paper provides an initial assessment of API deprecation in JavaScript by analyzing 50 popular software projects. Initial results suggest that the use of deprecation mechanisms in JavaScript packages is low. However, we find five different ways that developers use to deprecate API in the studied projects. Among these solutions, deprecation utility (i.e., any sort of function specially written to aid deprecation) and code comments are the most common practices in JavaScript. Finally, we find that the rate of helpful message is high: 67% of the deprecations have replacement messages to support developers when migrating APIs.

1. JavaScript API Deprecation in the
Wild: A First Assessment
Romulo Nascimento, Aline Brito, Andre Hora, Eduardo Figueiredo
IEEE SANER 2020

2. Motivation
JavaScript is the most popular
programming language for the seventh
consecutive year
2

3. Motivation


GitHub also reports JavaScript as a
popular language

3

4. There are several JavaScript libraries
Lodash
Axios
Angular
4

5. There are several JavaScript libraries
Lodash
Axios
Angular
5
Library for
static analysis

6. There are several JavaScript libraries
Lodash
Angular
6
HTTP client
Axios

7. There are several JavaScript libraries
Axios
Angular
7
Utility library
Lodash

8. Library services are provided via APIs



8

9. Libraries and their APIs evolve over time
9

10. API Deprecation
Deprecation mechanisms help clients to
migrate to new API versions
10

11. Example of API Deprecation


11

12. Example of API Deprecation


The question has
17K views
12

13. Example of API Deprecation


13

14. Example of API Deprecation


A developer recommends
two options
14

15. Example of API Deprecation


JSDoc deprecated
annotation
15

16. Example of API Deprecation


Console warning
message
16

17. How do developers
actually deprecate
JavaScript APIs?
17

18. Outline
18
1.Dataset
2.Searching for deprecation occurrences
3.Results

19. Dataset
19

20. Dataset
20
50 popular JavaScript projects
Metrics from GitHub repositories

21. Searching for Deprecation
Occurrences
21

22. We downloaded the source code of the 50 projects
(latest stable version)
22

23. We downloaded the source code of the 50 selected projects
(latest stable version)
We discarded files that are not part of the core systems
23

24. We downloaded the source code of the 50 selected projects
(latest stable version)
We discarded files that are not part of the core systems
We used a regular expression to find deprecation occurrence
candidates
24

25. We downloaded the source code of the 50 selected projects
(latest stable version)
We discarded files that are not part of the core systems
We used a regular expression to find deprecation occurrence
candidates
25
29 projects (58%)

26. Results
26

27. RQ1: How do Developers
Deprecate JavaScript APIs?
27

28. How do Developers Deprecate JavaScript APIs?
DATASET
1,279 deprecation
contexts
29 project (58%)
28

29. How do Developers Deprecate JavaScript APIs?

DATASET
29 project (58%) 1,279 deprecation
contexts
29

30. How do Developers Deprecate JavaScript APIs?

1,279 deprecation
contexts
We selected a
random sample of
268 cases (20%) for
manual analysis

30

31. How do Developers Deprecate JavaScript APIs?


Deprecation
utility
Code
comment
JSDoc
/* */
Console Deprecation
lists
31

32. How do Developers Deprecate JavaScript APIs?


Deprecation
utility
Any set of code functions to
aid code deprecation

88 occurrences (33%)
32

33. How do Developers Deprecate JavaScript APIs?


Code
comment
/* */
Use of code comments
excluding occurrences of JSDoc

27 occurrences (10%)
33

34. How do Developers Deprecate JavaScript APIs?


JSDoc
Use of the
JSDoc annotation

22 occurrences (8%)
34

35. How do Developers Deprecate JavaScript APIs?


Deprecation
lists
List of deprecated elements


18 occurrences (7%)
35

36. How do Developers Deprecate JavaScript APIs?


Console
Use of the JavaScript engine
native console API


11 occurrences (4%)
36

37. RQ2: Are JavaScript APIs
Deprecated with Replacement
Messages?
37

38. Are JavaScript APIs deprecated with
replacement messages?

67%

Replacement messages to support developers to
migrate to new versions

38

39. Example: Replacement Message
39
handleExceptions(...args){
...
console.warn('Deprecated:
.handleExceptions() will be removed in
winston@4. Use .exceptions.handle()' )
...
}

40. Example: Replacement Message
40
handleExceptions(...args){
...
console.warn('Deprecated:
.handleExceptions() will be removed in
winston@4. Use .exceptions.handle() ')
...
}

41. Are JavaScript APIs deprecated with
replacement messages?
Deprecation
utility
75 occurrences of
replacement messages


41

42. Code
comment
/* */
4 occurrences of
replacement messages


Are JavaScript APIs deprecated with
replacement messages?
42

43. Are JavaScript APIs deprecated with
replacement messages?
JSDoc
10 occurrences of
replacement messages


43

44. Conclusion and Discussion
44

45. Conclusion and Discussion


Deprecation adoption is not frequent in
JavaScript APIs
Only 3% of all analyzed files contain
occurrences of deprecation mechanisms
45

46. Conclusion and Discussion



Only 22 occurrences (8%) of JSDoc
JSDoc is not popular among deprecation
mechanisms
46

47. Future Studies
Survey with API developers about
motivation and impressions behind the
usage of JavaScript deprecation practices
47

48. Future Studies
Tool
Identification of
deprecation contexts

Alert about missing
replacement messages


48

49. JavaScript API Deprecation in the
Wild: A First Assessment
Romulo Nascimento, Aline Brito, Andre Hora, Eduardo Figueiredo
IEEE SANER 2020