How can I install it?

Via npm:

npm i -S chekify

Or if you just want the git repo:

git clone https://github.com/EugeneHerasymchuk/checkify.git

How can I use it?

You should require ('checkify').

var it = require('checkify');

Then it's easy to use it like in ordinary language:

it.hasFirstCapital('Node'); //true

it.hasOnlyLetters('Node'); //true

it.isBlank(''); //true

it.isNumber(42); //true

it.isString('Node'); //true

it.isBoolean(3==='w'); //interesting... but true

it.isArray(['npm', 'Node']); //true

it.isNan(Math.sqrt(-1)); //true

it.isFn(function(){}); //true

it.isDate(new Date); //true

Even you can check whole sentenses if it has bAd wOrdS. Add them using:

it.addBadWords(['my', 'BAD', 'words']);

Check it!!

it.hasBadWords('your sentences with BAD words') //true