Improve page rendering by deferring disqus loading

[KaitoHH]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines.
• Tests for the changes was maked (for bug fixes / features).
  • Muse | Mist have been tested.
  • Pisces | Gemini have been tested.
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PR Type

What kind of change does this PR introduce?

• Bugfix.
• Feature.
• Code style update (formatting, local variables).
• Refactoring (no functional changes, no api changes).
• Build related changes.
• CI related changes.
• Documentation content changes.
• Other... Please describe: Improvement

What is the current behavior?

The whole web page is blocked and shows nothing until loading embed.js for Disqus is completed. Things get worse when some users (especially those Chinese users) have trouble connecting Disqus since they will see a blank page for a long time until the requested timeout.

In addition, for those who enable pace.js, they will see the progress bar circling for a long time until timeout.

What is the new behavior?

The main cause of this problem is that loading *.js for Disqus blocks the rendering of the whole web page, so I simply defer the js loading until the whole page loading is completed.

hexo-theme-next/layout/_third-party/comments/disqus.swig

Line 10 in 54a04c6

window.addEventListener('load', loadCount, false);

Here I use window.onload callback function instead of directly inserting script tag to prevent blocking the whole web page.

Does this PR introduce a breaking change?

• Yes.
• No.

[CLAassistant]

All committers have signed the CLA.

[stevenjoezhang]

How about disqusJS? #705

[KaitoHH]

Fixed. Notice that DisqusJS also has the same problem as #395. So I fixed it by adding essential url and identifier attribute.

hexo-theme-next/layout/_third-party/comments/disqusjs.swig

Lines 18 to 19 in 98c3083

	url: {{ page.permalink | json }},
	identifier: {{ page.path | json }},

[1v9]

@allcontributorsadd please add @KaitoHH for code

[allcontributors]

@1v9

I've put up a pull request to add @KaitoHH! 🎉