How to "uniqueify" a javascript array of objects?

Question

How does one remove objects in an array that match across all keys and values? I've seen variations of this question but only for a particular field.

For example, given the following input the output would look like so:

> var a = [
  {a:1, b:'x'},
  {a:1, b:'y'},
  {a:1, b:'y'},
  {a:2, b:'x'},
  {a:2, b:'y'},
  {a:2, b:'y'},
  {a:2, b:'x'},
  {b:'y', a:2},
  {a:2, b:'y', c:'surprise!'}
]
> blackbox(a)
[
  {a:1, b:'x'},
  {a:1, b:'y'},
  {a:2, b:'x'},
  {a:2, b:'y'},
  {a:2, b:'y', c:'surprise!'}
]

Ideally blackbox isn't hard-coded with the keys.

keithpjolley · Accepted Answer · 2018-06-23 19:47:10Z

1

BTW, here the hack that I have now. It turns each (sorted) object into a string and checks to see if it's seen that string before.

Regardless, there's got to be a more elegant solution out there!

> function uniq(a) {
  var keys = new Set();
  return a.filter(function(row) {
    var key  = Object.entries(row).sort().toString();
    var uniq = !keys.has(key);
    keys.add(key);
    return uniq;
  });
}
> a =
[ { a: 1, b: 'x' },
  { a: 1, b: 'y' },
  { a: 1, b: 'y' },
  { a: 2, b: 'x' },
  { a: 2, b: 'y' },
  { a: 2, b: 'y' },
  { a: 2, b: 'x' },
  { b: 'y', a: 2 },
  { a: 2, b: 'y', c: 'surprise!' },
  { c: 'surprise!', a: 2, b: 'y' } ]
> uniq(a)
[ { a: 1, b: 'x' },
  { a: 1, b: 'y' },
  { a: 2, b: 'x' },
  { a: 2, b: 'y' },
  { a: 2, b: 'y', c: 'surprise!' } ]
> b =
[ { a: { b: 1, c: 2 }, b: 1 },
  { b: 1, a: { c: 2, b: 1 } },
  { a: { b: 1, c: 2 }, b: 2 } ]
> uniq(b) // works because nested objects happen to be identical
[ { a: { b: 1, c: 2 }, b: 1 }, { a: { b: 1, c: 2 }, b: 2 } ] 
> c = 
[ { a: { b: 1, c: 2 }, b: 1 },
  { b: 1, a: { c: 2, b: 1 } },
  { a: { b: 1, c: 2 }, b: 2 },
  { a: { b: 2, c: 1 }, b: 2 } ]
> uniq(c) // fail on nested object
[ { a: { b: 1, c: 2 }, b: 1 }, { a: { b: 1, c: 2 }, b: 2 } ]

edited Jun 23, 2018 at 19:47

answered Jun 23, 2018 at 19:35

keithpjolley

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2 Comments

Gerardo BLANCO Over a year ago

This should be an edit to your question, not an answer

keithpjolley Over a year ago

It's an answer because it answers a specific use case that I think will be useful. I'm hoping that there are better answers that are more general and more elegant.

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