Array.prototype.unique

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What about using ~ instead of <0?

try it and you'll see why. ;)

Got it. Well, then how about

Array.prototype.unique=[].unique||function(a,b){for(a=this,b=a.length;b--;a.indexOf(a[b])<b&&a.splice(b,1));return a}

does not forcefully overwrite the original method and is still 3 bytes shorter.

it may be shorter, but it's also destructive. probably not a good idea for something like unique.

A bit longer (133 chars), but not destructive:

Array.prototype.unique||(Array.prototype.unique=function(a,b){for(a=this,b=a.length;b--;a.indexOf(a[b])<b&&a.splice(b,1));return a})

Or if you want to use your filter version (even shorter), take one of the anonymous functions out of the closure:

Array.prototype.unique||(Array.prototype.unique=function(){return this.filter(function(a,b,c){return c.indexOf(a,b+1)<0})})

this isn't an ES5 shim, so i'm not sure we need to worry about overwriting anything. by destructive i mean that your version mutates the original array.

Ah, well, then at least the removal of the closure should bring some less bytes.

well, given it's a bit of an expensive operation, i'd prefer the caching of the function. @WebReflection has a really good sense for that stuff.

hi. awesome function, thanks on that!

on a = [ 1,2,3,4,3,2,1] your version returns
[4, 3, 2, 1]
which might be disappointing if we want to have the first occurrence to be first in result set

so if you do it like that
Array.prototype.unique=function(a){return function(){return this.filter(a)}}(function(a,b,c){return c.indexOf(a)==b})
it'll return
[1, 2, 3, 4]

of course it might affect performance

thanks again!

[1,2,3,1].reduce((acc, item) => acc.includes(item) ? acc : acc.concat(item), [])
is simpler

Array.prototype.uniq =
Array.prototype.unique = 
  ( () => function()
    { return [ ...new Set( this ) ] } 
  ) ()