json array with null

Question

Below is the JSON that is parsed to validate PUT request body:

{
    "requestKey": "whatever",
    "shoppingList": []
}

---

As part of testing, we are seeing another scenario coming, which is also a valid JSON:

{
    "requestKey": "whatever",
    "shoppingList": [null]
}

---

[] signifies empty shopping list. What does [null] signify?

How [null] different from []? for shoppingList

Answer 1

null in this case and as referenced in RFC 7159 means that the shoppingList is an array containing one primitive null value.

At least semantically it should yield in (Source example is in Java):

shoppingList.get(0) -> null 

Whereas an empty array should yield in:

shoppingList.get(0) -> IndexOutOfBoundsException

Which is exactly the behaviour you see in the current version of Google Chrome:

let myObj = {
    "requestKey": "whatever",
    "shoppingList": [null]
};
undefined
myObj
{requestKey: 'whatever', shoppingList: Array(1)}requestKey: "whatever"shoppingList: Array(1)0: nulllength: 1[[Prototype]]: Array(0)[[Prototype]]: Object
let myObj = {
    "requestKey": "whatever",
    "shoppingList": []
};
undefined
myObj
{requestKey: 'whatever', shoppingList: Array(0)}requestKey: "whatever"shoppingList: [][[Prototype]]: Object