Travis build: 1808

README.md

@@ -209,6 +209,7 @@ average(1, 2, 3);
 * [`off`](#off)
 * [`on`](#on)
 * [`onUserInputChange`](#onuserinputchange-)
+* [`prefix`](#prefix)
 * [`recordAnimationFrames`](#recordanimationframes)
 * [`redirect`](#redirect)
 * [`runAsync`](#runasync-)
@@ -3442,6 +3443,36 @@ onUserInputChange(type => {
 <br>[⬆ Back to top](#table-of-contents)
 
 
+### prefix
+
+Returns the prefixed version (if necessary) of a CSS property that the browser supports.
+
+Use `Array.findIndex()` on an array of vendor prefix strings to test if `document.body` has one of them defined in its `CSSStyleDeclaration` object, otherwise return `null`. 
+Use `String.charAt()` and `String.toUpperCase()` to capitalize the property, which will be appended to the vendor prefix string.
+
+```js
+const prefix = prop => {
+  const capitalizedProp = prop.charAt(0).toUpperCase() + prop.slice(1);
+  const prefixes = ['', 'webkit', 'moz', 'ms', 'o'];
+  const i = prefixes.findIndex(
+    prefix => typeof document.body.style[prefix ? prefix + capitalizedProp : prop] !== 'undefined'
+  );
+  return i !== -1 ? (i === 0 ? prop : prefixes[i] + capitalizedProp) : null;
+};
+```
+
+<details>
+<summary>Examples</summary>
+
+```js
+prefix('appearance'); // 'appearance' on a supported browser, otherwise 'webkitAppearance', 'mozAppearance', 'msAppearance' or 'oAppearance'
+```
+
+</details>
+
+<br>[⬆ Back to top](#table-of-contents)
+
+
 ### recordAnimationFrames
 
 Invokes the provided callback on each animation frame.

snippets/prefix.md

@@ -9,9 +9,11 @@ Use `String.charAt()` and `String.toUpperCase()` to capitalize the property, whi
 const prefix = prop => {
   const capitalizedProp = prop.charAt(0).toUpperCase() + prop.slice(1);
   const prefixes = ['', 'webkit', 'moz', 'ms', 'o'];
-  const i = prefixes.findIndex(prefix => typeof document.body.style[(prefix ? prefix + capitalizedProp : prop)] !== 'undefined');
+  const i = prefixes.findIndex(
-  return i !== -1 ? i === 0 ? prop : prefixes[i] + capitalizedProp : null;
+    prefix => typeof document.body.style[prefix ? prefix + capitalizedProp : prop] !== 'undefined'
-}
+  );
+  return i !== -1 ? (i === 0 ? prop : prefixes[i] + capitalizedProp) : null;
+};
 ```
 
 ```js