create an array of unique values in JavaScript

解法1:

let uniqueArray = [...new Set([5,5,2,2,2,4,2])];

或

let uniqueArray = [...new Set(dupeArray)];

解法2:

let dupeArray = [3,2,3,3,5,2];
let uniqueArray = Array.from(new Set(dupeArray));

解法3:

if(this.items.indexOf(item) === -1) {
    this.items.push(item);
    console.log(this.items);
}