The simplest feature-detect for flexbox?

feature-detect flexbox.js

/*
 * Trying to feature-detect (very naive)
 * CSS Flexbox support. 
 * - Only most modern syntax
 * 
 * Is this nonsense?
 */

(function NaiveFlexBoxSupport(d){
  var f = "flex", e = d.createElement('b');
  e.style.display = f;
  return e.style.display == f;
})(document);

Wrote a version of Davids script that returns a boolean

export const testFlexbox = () => {
  const f = 'flex';
  const fw = `-webkit-${f}`;
  const el = document.createElement('b');

  try {
    el.style.display = fw;
    el.style.display = f;
    return !!(el.style.display === f || el.style.display === fw);
  } catch (err) {
    return false;
  }
};

Or you could make it css property generic

function cssPropertySupported(pNames) {
	const element = document.createElement('a')

	let index = pNames.length

	try {
		while (index--) {
			const name = pNames[index]

			element.style.display = name
			if (element.style.display === name) {
				return true
			}
		}
	} catch (pError) {}

	return false
}

cssPropertySupported(['-webkit-box', '-ms-flex', 'flex'])

according to mcshaman post:

cssPropertySupported(['-webkit-box', '-ms-flex', 'flex'])

should be:
cssPropertySupported(['-ms-flexbox', '-webkit-box', 'flex'])

By the way:

return true

should be:
return name

so you know what syntax is used