f=
a=>[...new Set(a.filter((b,c)=>a.indexOf(b)<c))];

tests=[
    [1,2,3],
    [1,2,3,2,1],
    [1.0, 2, 2.0, 1.0],
    [1, '1', '1.0'],
    [undefined, undefined, false, false, true, true],
    [1,2,1,1,1,2,1,2,2,1,1]
]
console.log(tests.map(b=>f(b)))