let data = [
{id: 1, serial: "Blood.Drive", season: 1},
{id: 2, serial: "Blood.Drive", season: 1},
{id: 3, serial: "Foo.Bar", season: 1},
{id: 4, serial: "HelloWorld", season: 1},
]
let unique = data.reduce((acc,elem)=>acc.add(elem.serial), new Set())
console.log(unique)
https://jsfiddle.net/9Lunhds9/