Array.push() and unique items

Question

I have a simple case of pushing unique values into array. It looks like this:

  this.items = [];

  add(item) {
    if(this.items.indexOf(item) > -1) {
           


        

Answer 1

try .includes()

[1, 2, 3].includes(2);     // true
[1, 2, 3].includes(4);     // false
[1, 2, 3].includes(3, 3);  // false
[1, 2, 3].includes(3, -1); // true
[1, 2, NaN].includes(NaN); // true

so something like

const array = [1, 3];
if (!array.includes(2))
    array.push(2);

note the browser compatibility at the bottom of the page, however.