Javascript create array of objects of length n [duplicate]

Question

Is there a one-liner to create an array of objects of length n?

const arr = [
    { first_name: '', last_name: '' },
    { first_name: '', last_name: '' },
    { first_name: '', last_name: '' },
]

I've tried below but am getting SyntaxError: unexpected token: ':'

const arr = [...Array(3).map(x => { first_name: '', last_name: '' })]

Answer 1

You need to wrap return value by () whenever you want to return object from arrow function you need to wrap () else it will treat it as start of function body,

console.log([...Array(3).map(x => ({ first_name: '', last_name: '' }))])

Now you see error is gone but why the values are undefined ? because map doesn't loop over the empty slots you need to use fill

console.log([...Array(3).fill(0).map(x => ({ first_name: '', last_name: '' }))])

Or you can use Array.from

let arr = Array.from({ length: 3 } , () => ({ first_name: '', last_name: '' }))

console.log(arr)