My use case was an array of objects coming from a document-store so they're extremely variable and we only want a sub-set of the returned fields. There are plenty of ways to go about this and I hope snippet will serve that purpose, but for me this was more about realizing the power of () to do a bit more with the Lambda passed to map(). I regularly pull up ANY chrome page, hit Ctrl+Shift+J and develop small snippets right in the console, which is what led to 1 of 2 discoveries today.
let result = { Items: [{ a: 1, b: 2, x: 3 }] },
newList = result.map( o => { return { a: o.a, b: o.b }; );