add exercise files

[JerGerr]

No description provided.

[bch-fullstack]

Please make the following changes before your pull request can be approved:
Ex1:
Line 1:
Array.isArray(input){ should be a function declaration
The correct script should have been
function isArray(input){

Ex2
for now, lets stick to declaring function in the normal way as following
function first(array, n) {... // line 1
instead of as an var
Please use curly brackets to wrap the content of your if statements and use triple equal sign === instead of ==
so if (array === null) { return void 0; } ...

Ex3.
Please also wrap your loop content within curly brackets and beautify your code before committing to fix the indentation

Ex4. Good job. However try to play around with !~pin.indexOf('.') statement, I personally prefer to use pin.indexOf('.') > -1