Web-distribution of plain-old HTML/JS/CSS solution in Office 365

One of the many capabilities of SharePoint is that of webserver platform: host and distribute HTML/JavaScript/CSS based (mini)applications. With the birth of the SharePoint Framework (SPFx), I expect this role to be utilized a lot more in near future. The typical SharePoint setup for this web-distribution role is 1) a SharePoint page, 2) a ScriptEditor (or good-old ContentEditor webpart), and 3) the (mini)application itself consisting of an html-file for UI, potential javascript and/or css file(s), all stored as (SharePoint) content entities in a document library, or in a CDN.

SharePoint Online / Office 365 also supports this setup, and thus should be an equal fit for the role of web-distribution. However, you need to be aware of 3 aspects:

1. Default, custom script is not allowed in Office 365 tenant.

   You'll notice the effect of this when you try to add custom script in a ScriptEditor, or on using PageViewer webpart which refuses to remember the url to the (mini)application html file - (Office 365 SharePoint Online - Page Viewer Web Part Not Working)

   The resolution is to set in SharePoint Online Admin settings the allowance for custom script - (Turn scripting capabilities on or off). Be aware that it can take up to 24 hours before the effect of the change is actually applied in your Office 365 tenant.

2. ContentEditor prohibits 'FORM'tags in content:

   

   The resolution is to indeed use a PageViewer webpart, that is if the HTML contains a FORM tag. If not, good old CEWP accept the HTML as included content.

3. SharePoint Online only supports download action on .htm(l) file

   The Microsoft SharePoint team made an explicit design decision to only allow download of html files, and no rendering in browser - (Office 365 - Open html document in browser in document library).

   The simple resolution is to change the extension of the .htm(l) files into .axpx, then SharePoint (Online) will no longer include the "X-Download-Options: noopen" header in the HTTP response, and the file is opened in the browser rendering the html code.