array-union 
Create an array of unique values, in order, from the input arrays
Install
$ npm install --save array-union
Usage
const arrayUnion = require('array-union');
arrayUnion([1, 1, 2, 3], [2, 3]);
//=> [1, 2, 3]
arrayUnion(['foo', 'foo', 'bar'], ['foo']);
//=> ['foo', 'bar']
License
MIT © Sindre Sorhus