Tree.

filter(tree, options)

Applies a filter operation to a tree, returning only those values that pass a test function.

The options parameter can be either a function that will be used as the test function or a dictionary of options:

  • deep: a boolean (default: false) indicating whether the filter should be applied deeply
  • test: a function to use to test values for inclusion

The test function will be called with the value, key, and tree of each key/value in the tree. The test function should return a truthy result if the value should be included in the result of the filter operation.

See also Tree.mask.

Example #

The filter operation can be used, for example, to filter a set of blog posts and return only published blog posts — those with a false or missing draft property. This would commonly be applied to a set of post files, but for illustration purposes can be applied to a small data set in a YAML file:

# posts.yaml
- title: Post 1
  _body: This is the first post
- title: Post 2
  draft: true
  _body: This is the second post

The filter operation returns true if the draft property is missing or false:

// published.ori
Tree.filter(posts.yaml, (post) => !post.draft)

Applying this to the posts returns just the published posts:

$ ori published.ori/
- title: Post 1
  _body: This is the first post