JS: Null-Safe Array Concat

Question

Given:

var a = [1, 2, 3]
var b = null

I need to:

var c = [...a, ...b]

.. but that does not work when a or b is null of course. So in this example b should just not be added, resulting in c = [1, 2, 3]. If both aand b are null (or undefined), the result should be [].

Are there any shorthands to avoid having to write two if-statements?

Answer 1

You could make use of the || operator.

var a = [1, 2, 3]
var b = null

var c = [...a||[], ...b||[]]

console.log(c)

Answer 2

var c = [...(a || []), ...(b || [])]

This way if any array is null or undefined it will be replaced by an empty array

Answer 3

You can use filter

var a = [1, 2]
var b = null
var c = [3, null, 4]

var d = []
d.concat(a,b,c).filter(item => item !== null) // [1, 2, 3, 4]

console.log("Array", d)