Merge pull request #54 from fhdhsni/master

Add bottomVisible

README.md

@@ -11,6 +11,7 @@
 
 * [Anagrams of string (with duplicates)](#anagrams-of-string-with-duplicates)
 * [Average of array of numbers](#average-of-array-of-numbers)
+* [Bottom visible](#bottom-visible)
 * [Capitalize first letter of every word](#capitalize-first-letter-of-every-word)
 * [Capitalize first letter](#capitalize-first-letter)
 * [Chain asynchronous functions](#chain-asynchronous-functions)
@@ -92,6 +93,23 @@ const average = arr =>
 // average([1,2,3]) -> 2
 ```
 
+### Bottom visible
+
+Returns `true` if bottom of the page is visible. It adds `scrollY` to
+the height of the visible portion of the page (`clientHeight`) and
+compares it to `pageHeight` to see if bottom of the page is visible.
+
+```js
+const bottomVisible = () => {
+  const scrollY = window.scrollY;
+  const visibleHeight = document.documentElement.clientHeight;
+  const pageHeight = document.documentElement.scrollHeight;
+  const bottomOfPage = visibleHeight + scrollY >= pageHeight;
+
+  return bottomOfPage || pageHeight < visibleHeight;
+}
+```
+
 ### Capitalize first letter of every word
 
 Use `replace()` to match the first character of each word and `toUpperCase()` to capitalize it.

snippets/bottom-visible.md

@@ -0,0 +1,9 @@
+### Bottom visible
+
+Use `scrollY`, `scrollHeight` and `clientHeight` to determine if the bottom of the page is visible.
+
+```js
+const bottomVisible = _ => 
+  document.documentElement.clientHeight + window.scrollY >= document.documentElement.scrollHeight || document.documentElement.clientHeight;
+// bottomVisible() -> true
+```