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);

I have wrapped it in a try/catch and added a -webkit- prefix check, now Safari 7.1 returns true. Need tidying up, obvs.

(function(d){
  var c = " ", f = "flex", fw = "-webkit-"+f, e = d.createElement('b');
  try { 
    e.style.display = fw; 
    e.style.display = f; 
    c += (e.style.display == f || e.style.display == fw) ? f : "no-"+f; 
  } catch(e) { 
    c += "no-"+f; 
  }
  d.documentElement.className += c; 
})(document);

This is a cool concept but where is the return in the updated code?

There is no return statement because @davidhund is adding a class of 'flex' or 'no-flex' to the html tag.

Very interesting. Just want to point out that, for the most part, if it's Flexbox-compatible, there really isn't anything I need to do in CSS.

However, if its Flexbox-incompatible, I need to add additional CSS. In that case, I would want to add a class to HTML to tell me its incompatible so I can take advantage of the cascading nature of CSS.

opps - I see it's supposed to add "no-flex." It does not do that in IE emulation in MS Edge.

When emulating IE9 and IE10 it adds "flex" contrary to the compatibility chart above.

Thank's for you help. I wrote this code for you:

(function(d) {
        'use strict';
        var c = " ", prefixFlex = 'flex -webkit-flex -ms-flexbox -moz-box -webkit-box'.split(' '), elem = d.createElement('b'), mStyle = elem.style;
        try {
            for (var i = 0, len = prefixFlex.length; i < len; i++) {
                c += ( (mStyle.display = prefixFlex[i]) && mStyle.display != prefixFlex[i] ) ? 'no-flex' :  'flex', (i = len);
            }
        } catch(e) { 
            c += "no-flex";
        }
        d.documentElement.className =  c + 'box';
    })(document);

Just curious in what circumstances this will cause an error. I'm assuming it can cause an error since you added the try/catch block.

@brentonstrine, I think it's IE8 (per @davidhund's answer: https://gist.github.com/davidhund/b995353fdf9ce387b8a2#gistcomment-1317135)

David, how about this solution?
https://github.com/ergcode/ergonomic.detect_flex

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