Elasticsearch and express.js - Find and update nested property in document - node.js

Question

Successfully I found how to implement adding an element to nested property list, but currently I'm struggling with Elasticsearch mechanisms of updating document properties. I'm trying to update using Axios as my main library of wrapping of HTTP client. An example of saved documents in Elasticsearch:
{
"took": 4,
"timed_out": false,
"_shards": { "total": 1, "successful": 1, "skipped": 0, "failed": 0 },
"hits": {
"total": { "value": 2, "relation": "eq" },
"max_score": 1.0,
"hits": [
{
"_index": "my-index-01",
"_type": "_doc",
"_id": "-8_MhnsBRfQBiuhMDxjT",
"_score": 1.0,
"_source": {
"code": "ABC",
"description": "Test",
"items": [{ "key": "XYZ", "value": "123" }]
}
},
{ ... },
{ ... },
{ ... }
]
}
}
My main goal is to filter from _source element by code field and get from items table element by key and then change the value.
I tried with this code but the value is not changing and I'm getting en 400 response from my docker Elasticsearch container:
const input = {
key: "XYZ",
value: "1234"
}
this.axios.post(
`/my-index-01/_update_by_query`,
{
script: {
lang: 'painless',
source: `if (ctx._source.items['items.key'].value.key == params.key) {
doc['items.key'].value.value == params.value;
} `,
params: input
},
query: {
match: {
code: "ABC",
},
}
},
{
headers: {
"Content-Type": "application/json",
},
}
);

Answer 1

I found a solution to this problem. I want to share it here as answer, maybe someday someone will struggle with the same issue:
this.axios.post(
`/my-index-01/_update_by_query`,
{
script: {
lang: 'painless',
source: `for (def item : ctx._source.items) {
if (item.key == params.key) {
item.value = params.value;
}
} `,
params: input
},
query: {
match: {
code: "ABC",
},
}
},
{
headers: {
"Content-Type": "application/json",
},
}
);