// dependencies, timing and global options
dependencies: ['sheet.css'], // wait for sheet.css via dependencies and insert after DOM element
selector: '#footer', // download stylesheet when footer becomes visible within 250 pixels
type: 'media', // download stylesheet based on a media query (also works with viewport changes)
media: 'screen and (max-width: 600px)'
{ // global options applied to all stylesheets
base: '/long/path/to/css/', // base directory for relative sheet URLs
max_size: 10000, // cache only <10kb
fallback: 'cache-api', // fallback to Cache-API for bigger sheets
head: true, // use HTTP HEAD request to check for 304 - Not Modified
interval: 86400 // update once per day
source: ['cssText','xhr','cors'], // default
proxy: 'https://cors-anywhere.herokuapp.com/', // more proxies on https://gist.github.com/jimmywarting/ac1be6ea0297c16c477e17f8fbe51347
"x-special-header": "secret-key" // request header to include in XHR requests
"data-app-sheet": "1" // HTML attribute to add to stylesheet element
render_timing: 'requestAnimationFrame' // render via requestAnimationFrame
).then(function() { /* ready */ });