Parse CSS in a browser

parse-css.js

var style = document.createElement('style')
var iframe = document.createElement('iframe')
document.body.appendChild(iframe)
iframe.contentDocument.documentElement.appendChild(style)
iframe.style.display = 'none'

style.textContent = 'a {color: red}'
style.sheet // CSSStyleSheet
style.sheet.cssRules[0].cssText // 'a { color: red; }'
style.sheet.cssRules[0].selectorText // 'a'
style.sheet.cssRules[0].style[0] // 'color'
style.sheet.cssRules[0].style.color // 'red'