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unique: remove duplicates

Write a function unique(array) that returns a new array without repeats, keeping the order of first appearance.

NaN should collapse into one element too, and objects are compared by reference.

function unique(array) {
  // ...
}

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Tests (5)

expect(unique([1, 2, 2, 3, 1])).toEqual([1, 2, 3]);

expect(unique(["b", "a", "b"])).toEqual(["b", "a"]);

expect(unique([NaN, NaN, 0, -0])).toEqual([NaN, 0]);

const obj = {};
expect(unique([obj, obj, {}]).length).toBe(2);

const source = [1, 1];
unique(source);
expect(source).toEqual([1, 1]);