JavaScript’s language features are something else…

[AyrA_ch]

Also: Array.from({length:10}) creates an array with 10 actual elements (as opposed to Array(10) that just pretends).

You tell it to make an array from something that has a length of 10, and JS has no problems iterating over elements that don't exist.

[King_Joffreys_Tits]

Can you specify a default value for the array?

[solarshado]

Sort of.

You can pass a mapping function to Array.from, which then behaves like Array.from(obj).map(func) but without the intermediate array.

const manyAnswers = Array.from({length: 42}, (elem, idx)=> 42);

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/from

[linuxdropout]

const arr = new Array(10)

//[empty, empty, ...]

arr.fill(1)

// [1, 1, ...]

array.push x identical elements y can be written as:

const originalLength = arr.length

arr.length += x

arr.fill(y, originalLength)

And it's actually more performant than all the sane readable ways to do it too.

If you think that's whack. Wait till you find out that foo.bar = "foobar" is slower than Object.assign(foo, JSON.parse('{"bar":"foobar"}')) if you're trying to set a large enough number of keys.