stDeviation

A threshold of 1.0 means that when 100% of the target is visible within the element specified by the root option, the callback is invoked

The first time the observer is initially asked to watch a target element.

Some JS or a CSS animation causes a visual change, kicking off the rendering cycle.

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zero

In continuous media, the viewport is the viewing area of the browser window.

A couple of great use-cases for location state are: Telling the next page where the user came from and branching the UI. The most popular implementation here is showing a record in a modal if the user clicked on an item in a grid view, but if they show up to the URL directly, show the record in its own layout (pinterest, old instagram). Sending a partial record from a list to the next screen so it can render the partial data immediately and then fetching the rest of the data afterward.

That’s a pattern that repeats again and again: a solution is created in an imperative language and if it’s popular enough, it migrates to a declarative language over time. When a feature is available in a declarative language, not only is it easier to write, it’s also more robust.

Tim Berners‐Lee assumed that most URLs would point to non‐HTML resources; word‐processing documents, spreadsheets, and all sorts of other computer files. HTML could then be used to create simple index pages that point to these files using links. Because HTML didn’t need to do very much, it had a limited vocabulary. That made it relatively easy to learn. To Tim Berners‐Lee’s surprise, people began to create fully‐fledged documents in HTML. Instead of creating content in other file formats and using HTML to link them up, people began writing content directly in HTML.