good coding reference.

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// for ECMAScript 5
function onlyUnique(value, index, self) { 
    return self.indexOf(value) === index;
}
// usage example:
var a = ['a', 1, 'a', 2, '1'];
var unique = a.filter( onlyUnique ); 
// returns ['a', 1, 2, '1']
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// With ES6
// usage example:
var myArray = ['a', 1, 'a', 2, '1'];
var unique = myArray.filter(
        (v, i, a) => a.indexOf(v) === i
    ); 
// unique is ['a', 1, 2, '1']
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// With ES6, native Set
var myArray = ['a', 1, 'a', 2, '1'];
let unique = [...new Set(myArray)]; 
// unique is ['a', 1, 2, '1']