hubcap coverage

Get JavaScript code coverage data for the current page.

When to use

Use coverage to identify unused JavaScript code. For the most accurate results, run this after performing page interactions so that event handlers and lazy code paths are exercised. Use csscoverage for CSS rule coverage instead.

Usage

hubcap coverage

Arguments

None.

Flags

None.

Output

Returns JavaScript code coverage data for each script.

Field	Type	Description
[].scriptId	string	Identifier of the script
[].url	string	URL of the script
[].functions	array	Array of function coverage entries
[].functions[].functionName	string	Name of the function
[].functions[].ranges	array	Array of coverage ranges with start/end offsets and count

[
  {
    "scriptId": "42",
    "url": "https://example.com/app.js",
    "functions": [
      {
        "functionName": "init",
        "ranges": [
          {"startOffset": 0, "endOffset": 120, "count": 1}
        ]
      },
      {
        "functionName": "unusedHelper",
        "ranges": [
          {"startOffset": 121, "endOffset": 200, "count": 0}
        ]
      }
    ]
  }
]

Errors

Condition	Exit code	Stderr
Chrome not connected	2	`error: connecting to Chrome: ...`
Timeout	3	`error: timeout`

Examples

Get JavaScript coverage:

hubcap coverage

Find functions that were never called:

hubcap coverage | jq '[.[] | .functions[] | select(.ranges[0].count == 0) | .functionName]'

Interact with the page first, then measure coverage:

hubcap goto --wait "https://example.com" && hubcap click "#menu-toggle" && hubcap click "#submit" && hubcap coverage | jq '[.[] | {url, unused: [.functions[] | select(.ranges[0].count == 0)] | length}]'