Add elements inside Array conditionally in JavaScript

Question

When I try to merge two objects using the spread operator conditionally, it works when the condition is true or false:

let conditio         


        

Answer 1

false is not spreadable.

You need a spreadable object (the one where Symbol.iterator is implemented) which returns nothing, if spreaded.

You could use an empty array as default value. This works even if arr is falsy.

let condition = false;
let arr1 = ['value1'];
let arr2 = ['value2', ...(condition && arr || [])];

console.log(arr2);