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3

1st/2nd example is no union at all + 1st example blows up the stack for large Arrays + 3rd example is incredibly slow and consumes a lot of memory, since two intermediate Arrays have to be build + 3rd example can only be used for union with a known number of Arrays at compile time.
– user6445533
Commented Oct 10, 2016 at 10:13
so how you would do it ?
– David Noreña
Commented Oct 19, 2016 at 14:45
9

Note that for set can't deduplicate two objects that have the same key value pairs unless they are the same object references.
– Jun
Commented Jan 5, 2018 at 2:16
should be accepted answer for the modern of Javascript.
– Thanh Nguyen
Commented Mar 14, 2018 at 9:21
18

Does not work with an array of objects, as it'll only merge object references and doesn't care if the objects themselves are equal.
– W Biggs
Commented Mar 7, 2019 at 19:12

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Correct minor typos or mistakes
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create code fences with backticks ` or tildes ~
```
like so
```
add language identifier to highlight code
```python
def function(foo):
print(foo)
```
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