Mongo - Replace substring of array

Question

Im having trouble replacing a substring in some documents. This would be the example of one of the many similar documents:

{
"images" : [
    {
        "url" : "https://example/1234"
    },
    {
        "url" : "https://example/afaef"
    },
    {
        "url" : "https://example/abcdef"
    }
]}

I need to replace all the 'example' substrings for say 'newresult'

This is my approach

db.collection.find({'images.url':/.*example*/} , {'images.url':true, _id:false}).forEach(function(doc) {
doc.images.url = doc.images.url.replace('example', 'newresult');
db.collection.save(doc);});

However im getting many errors trying different forms of this like doc.images.url is undefined. Also tried some different yet still unsuccesful variations of this.

I would really appreciate some insights on what im doing wrong, or if theres a better way to do this. Thanks.

Does this answer your question? [How to replace substring in mongodb document](https://stackoverflow.com/questions/12589792/how-to-replace-substring-in-mongodb-document) — whoami - fakeFaceTrueSoul, Apr 03 '20 at 18:55
You can try answer from 'Xavier Guihot' on the same link, it should work for your case.. — whoami - fakeFaceTrueSoul, Apr 03 '20 at 18:57
Since the doc that you pass to `save` does not have an `_id` it will create a new document in the collection. Was that the intent? — Joe, Apr 03 '20 at 19:01

mickl · Accepted Answer · 2020-04-03T19:21:09.683

2

You can try some MongoDB solution but if it's one-off JS script then you're close, the only thing you're missing is that images is an array so you need to use .map() like below:

let doc = {
"images" : [
    {
        "url" : "https://example/1234"
    },
    {
        "url" : "https://example/afaef"
    },
    {
        "url" : "https://example/abcdef"
    }
]};

doc.images= doc.images.map(({url, ...rest}) => ({url: url.replace('example', 'newresult'), ...rest}));

console.log(doc);

edited Apr 03 '20 at 19:21

answered Apr 03 '20 at 18:55

mickl

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Mmm, isnt working. I think it could be because my doc is in the format of {"images":[...]} as opposed to "images":[...] ? – Andres Julia Apr 03 '20 at 19:01
can you `console.log(doc)` and paste it here? – mickl Apr 03 '20 at 19:05
It might also be that you're not retrieving `_id` so if you want to update current docs then you have to get rid of `_id: false` – mickl Apr 03 '20 at 19:08
[object BSON] is the output – Andres Julia Apr 03 '20 at 19:14
try `printjson(doc)` – mickl Apr 03 '20 at 19:16
{ "_id" : ObjectId("eafafa343"), "images" : [ { "url" : "example/..." }, { "url" : "example/.." }, { "url" : "example/aefeaf" } ] } – Andres Julia Apr 03 '20 at 19:19
This looks valid, please also remove `'images.url':true` and check my modified answer if you have more fields in `images` and try again – mickl Apr 03 '20 at 19:21

Mongo - Replace substring of array

1 Answers1