Use 'document.scripts' instead of document.getElementsByTagName

[perry-mitchell]

document.scripts preserves script-addition order, so we can add scripts in the HEAD as well as BODY.

Currently using getElementsByTagName fails if the script is placed in the HEAD.

EDIT: This is nicely discussed here, where the author mentions (discussing the getElementsByTagName alternative):

There are two situations where this snippet will fail, though. When a script is loaded asynchronously using <script async>, the order of script execution is uncertain. Therefore the document.getElementsByTagName() trick will not work, as it relies on the currently executed script being the last of that collection. The same holds true for <script>s that are not appended to the end of the document. In the future this might become less of a problem, as document.currentScript properly resolves async scripts.

[SpaceK33z]

Hi, thanks for this PR. A lot of people have this issue, also see #117. Your PR is almost there, but could you make it to work like this:

1. Use document.currentScript if available. This is the most reliable way to get the current script, and works in most browsers.
2. Fallback to document.scripts.
3. If that fails, throw an exception.

[perry-mitchell]

Thanks @SpaceK33z - Will update this as soon as I can 🙂

[perry-mitchell]

@SpaceK33z I've updated the PR - using document.currentScript as you said.

[SpaceK33z]

Thank you! I have some tiny nitpicks, but I'll fix those in a separate commit.