Why Do Some Script Tags Have Both `src` and Inline Content?

Understanding the Purpose of Dual Attributes in Script Tags

It is commonly observed that script tags in web pages can possess multiple attributes. An example of this can be seen in Google's 1 button script tag:

<script type="text/javascript" src="https://apis.google.com/js/plusone.js">
  {"parsetags": "explicit"}
</script>

This specific script tag features both a src attribute, indicating the external script to be loaded, and content directly written within the script tag itself. The question arises, what does this configuration mean and how does it operate?

Browser Handling and Google's Implementation

Different web browsers may handle this situation in distinct ways. Some browsers only execute the inline content if the external script referenced by the src attribute is loaded successfully. Others, however, attempt to execute the inline content even if the external script fails to load.

Due to the inconsistency and unreliability of this behavior, HTML5 discourages the practice of using dual attributes in script tags. Despite this guidance, Google, in this particular case, does not rely on any specific browser behavior.

The inline content within the Google script tag, {"parsetags": "explicit"}, is an object literal. Executing this object literal directly does not have any immediate impact or cause errors. Instead, Google's code examines the contents of the script tag itself, including the inline object, and adjusts its behavior accordingly.

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