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+**Never add items to array usin indexes. Never trust them!**
+
+Lets create an empty array, and check its length is `0`
+```
+  var arr = [];
+  arr.length; // 0
+```
+
+Lets add something to its first place:
+
+```
+  var arr = []
+  arr[0] = 'I am the first';
+  arr.length; // 1
+```
+
+Oh, what if...
+
+
+```
+  var arr = []
+  arr[3] = 'I am the first';
+  arr.length; // 4
+```
+
+```
+  var arr = []
+  arr[0] = 'I am the first';
+  arr[15] = 'actually, i am the second';
+  arr.length; // 16
+```
+
+***WTF?***
+
+Array actually looks like
+```
+["I am the first", empty × 14, "actually, i am the second"]
+```
+
+** Explanation **
+
+This is how array's `.length` works. It takes index of the last elemnt, and returns `index+1`.
+
+Use native array methods to add items to it: `push`, `unshift`.
+
+— [@dogusev][1]
+
+[1]:https://github.com/dogusev
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