重複削除、配列内、配列内オブジェクト両方。

-配列内の要素とキーを使った配列内オブジェクトに対する重複削除。
demo https://codepen.io/gnjo/pen/vwMROz

let fn={};
fn.setary=(ary,key)=>{
 return (!key)?Array.from(new Set(ary)):ary.filter((a,b,c)=>(c.findIndex((d)=>(a[key]===d[key]))=== b))
}
;
let a=[1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9]
let aa=fn.setary(a) 
console.log(aa)//[1,2,3,4,5,6,7,8,9]
;
let b=[{key:1,value:1},{key:2,value:1},{key:3,value:1},{key:1,value:1},{key:2,value:1}]
let bb=fn.setary(b,'key')
console.log(bb)//[{key:1,value:1},{key:2,value:1},{key:3,value:1}]
;