Filters

Filters enable solving noise issues in versions that cannot be addressed with direct selection or removal of content using selectors.

When filters are needed

Use filters when:

• Content selectors are insufficient, for example when noise appears within content that can’t be targeted with CSS selectors or range selectors with the select and remove properties.
• Content is dynamically generated, for example when elements change on each page load with changing classes or IDs that cannot be targeted with attribute selectors.
• Complex tasks are needed, for example when content transformation is required such as converting images to base64 to store them in the terms version or converting date-based content to a stable format (like “Updated X days ago” to “Last updated on YYYY-MM-DD”).

How filters work

Filters are JavaScript functions that can manipulate the DOM structure directly. They modify the document structure and content in-place.

Filter design principles

Filters should follow these core principles:

• Specific: target only the noise to remove. Avoid broad selectors that might accidentally remove important content.

  For example, if a filter converts relative dates to absolute dates, make sure to scope the targeted dates. This might translate to selecting with .metadata time, not time, which might also affect important effective dates within the terms content.

• Idempotent: filters should produce the same result even if run multiple times on their own output. This ensures consistency.

  For example, if a filter adds section numbers like “1.” to headings, it should check if the numbers already exist, to prevent “1. Privacy Policy” from becoming “1. 1. Privacy Policy” on repeated runs.

• Efficient: DOM queries should be optimised and filters should avoid unnecessary operations, processing only the elements needed.

  For example, if a filter updates timestamp elements with a specific class, using document.querySelectorAll('.timestamp') is more efficient than document.querySelectorAll('*') followed by filtering for timestamp elements.

• Safe: filters must not accidentally remove important content. The generated version should always be checked after adding a filter to ensure it still contains the whole terms content.