What is the primary function of the 'defer' attribute when added to a script tag?

Explanation

The 'defer' attribute instructs the browser to download the script in parallel without blocking HTML parsing. The script execution is then deferred until the entire HTML document has been fully parsed. This is distinct from 'async', which executes the script as soon as it finishes downloading, potentially interrupting the parsing process.

Key points

Defer prevents render-blocking behavior
Scripts with defer execute in document order
Async scripts execute as soon as they download

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What is the primary function of the ‘defer’ attribute when added to a script tag?