Nested filtering with jq - json

Question

First time user of jq and I'm wanting to filter out objects based on a value within them and I'm struggling to figure it out.
I have a big json file with lots of product data like what's below. I'm wanting to filter out based upon which website_ids they have.
Example Input:
[{
"product_id": "2",
"sku": "PROD2",
"name": "Product Name 2",
"set": "4",
"type": "simple",
"category_ids": {
"item": "15"
},
"website_ids": {
"item": [
"1",
"4"
]}
},{
"product_id": "3",
"sku": "PROD3",
"name": "Product Name 3",
"set": "4",
"type": "simple",
"category_ids": {
"item": "15"
},
"website_ids": {
"item": [
"1",
"2"
]}
}]
Desired output:
[{
"product_id": "2",
"sku": "PROD2",
"name": "Product Name 2",
"set": "4",
"type": "simple",
"category_ids": {
"item": "15"
},
"website_ids": {
"item": [
"1",
"4"
]}
}]
I've tried a few different things but I'm clearly just not getting it.
jq 'map(.website_ids.item[] | contains("4"))'
Gives me:
[
false,
true,
false,
false
]
Which seems to match the website_ids items I want, but I'm not sure how to get the full JSON object from that.
Any help would be super appreciated! Thanks.
EDIT:
I've used this and it works with my example:
map(select(.website_ids.item[] | contains("4")))
What I've realised is that my example and the file I was actually testing on have some differences.
Sometimes a product has this for the website_id items:
"website_ids": {
"item": "2"
}
Which results in the error:
Cannot iterate over string ("2")
Is there a way around this?

Answer 1

All you need to do is add a select call in your map function, like so:
jq 'map(select(.website_ids.item[] | contains("4")))'
After your edit, it's a bit more complicated, but it can be worked around by checking the type of .website_ids.item and then based off of that type, doing a contains check or a simple equality check:
map((select((.website_ids.item | type) == "array") | select(.website_ids.item[] | contains("4"))), (select((.website_ids.item | type) == "string") | select (.website_ids.item == "4")))
Here it is formatted a bit more readable:
map(
(select((.website_ids.item | type) == "array") | select(.website_ids.item[] | contains("4"))),
(select((.website_ids.item | type) == "string") | select (.website_ids.item == "4"))
)