Development

This page explains how to manage assets using the Juno SDK, including uploading, listing, counting, and deleting files within your application. It also covers configuration options for optimizing storage and access control.

note

To use these features, the Juno SDK must be installed and initialized in your app.

Upload asset

To upload an asset, use the following code:

import { uploadFile } from "@junobuild/core";

const result = await uploadFile({
  data,
  collection: "images"
});

The data parameter is the file you want to upload. This is typically selected using an HTML <input type="file" /> element.

The uploadFile function provides various options, including:

filename: By default, Juno uses the file's filename. You can overwrite this and provide a custom filename. Example: myimage.jpg.
fullPath: Juno will automatically compute the fullPath, which is the unique path that is used to make the asset available on the internet. The fullPath is the filename prefixed with / plus the related collection key. Example: /images/myimage.jpg.
headers: The headers can affect how the browser handles the asset. If no headers are provided Juno will infer the Content-Type from the file type.
encoding: The type of encoding for the file. For example, identity (raw) or gzip.

note

Uploading a file with the same name as an existing file will overwrite the previous file (assuming the uploader has write access to the previous file).
URL encoding is currently not supported on the Internet Computer. Therefore, it's important to keep in mind that your filename should not be encoded. That is why the library decodes the filename automatically.

Protected asset

While all assets can be found on the internet, it is possible to make their URL difficult to guess so that they remain undiscoverable (as long as they are not shared) and considered "private".

Juno achieves this by using an optional token query parameter.

import { uploadFile } from "@junobuild/core";
import { nanoid } from "nanoid";

const result = await uploadFile({
  data,
  collection: "images",
  token: nanoid()
});

Imagine a file "mydata.jpg" uploaded with a token. Attempting to access it through the URL "https://yoursatellite/mydata.jpg" will not work. The asset can only be retrieved if a token is provided: "https://yoursatellite/mydata.jpg?token=a-super-long-secret-id".

List assets

The listAssets function is used to retrieve assets from a specified collection.

import { listAssets } from "@junobuild/core";

const myList = await listAssets({
  collection: "my_collection_key"
});

Parameters

The function requires a collection and accepts various optional parameters, including a matcher (a regex applied to the assets fullPaths and descriptions), pagination options, and sorting order.

note

listAssets uses the same interface as listDocs. That is why the parameter matcher expect a value key to filter the assets according their fullPath.

collection (required)
- Description: The key of the collection from which assets are to be listed.
- Type: string
filter (optional)
- Description: An optional object that can be used to provide various parameters to filter assets.
a. matcher (optional)
- Description: An object used to filter assets based on their keys (fullPaths) or descriptions using regular expressions.
- Type: ListMatcher
```
interface ListMatcher {
  key?: string;
  description?: string;
  createdAt?: ListTimestampMatcher;
  updatedAt?: ListTimestampMatcher;
}
```
  - key: A regex to match against asset keys.
  - description: A regex to match against asset descriptions.
  - createdAt: A ListTimestampMatcher to filter assets based on their creation timestamp.
  - updatedAt: A ListTimestampMatcher to filter assets based on their last update timestamp.
- Type: ListTimestampMatcher can be used to specify criteria for timestamp matching.
```
type ListTimestampMatcher =
  | {
      matcher: "equal";
      timestamp: bigint;
    }
  | {
      matcher: "greaterThan";
      timestamp: bigint;
    }
  | {
      matcher: "lessThan";
      timestamp: bigint;
    }
  | {
      matcher: "between";
      timestamps: {
        start: bigint;
        end: bigint;
      };
    };
```
  - matcher: Specifies the type of timestamp comparison. Can be one of the following:
    - equal: Matches assets where the timestamp is exactly equal to the specified value.
    - greaterThan: Matches assets where the timestamp is greater than the specified value.
    - lessThan: Matches assets where the timestamp is less than the specified value.
    - between: Matches assets where the timestamp falls within a specified range.
  - timestamp: Used with equal, greaterThan, and lessThan matchers to specify the exact timestamp for comparison.
  - timestamps: Used with the between matcher to specify a range of timestamps. The range is inclusive of both the start and end values.
b. paginate (optional)
- Description: An object to control pagination of the results
- Type: ListPaginate
```
interface ListPaginate {
  startAfter?: string;
  limit?: number;
}
```
  - startAfter: A string key to start listing assets after this key.
  - limit: The maximum number of assets to return.
c. order (optional)
- Description: Control the sorting order of the results.
- Type: ListOrder
```
interface ListOrder {
  desc: boolean;
  field: ListOrderField;
}

type ListOrderField = "keys" | "updated_at" | "created_at";
```
d. owner (optional)
- Description: The owner of the assets.
- Type: ListOwner
```
type ListOwner = string | Principal;
```

Example

Usage of the parameters:

import { listDocs } from "@junobuild/core";

const myList = await listDocs({
  collection: "my_collection_key",
  filter: {
    matcher: {
      key: ".*.png$", // match assets with .png extension
      description: "holiday", // match description containing 'holiday'
      createdAt: {
        matcher: "greaterThan",
        timestamp: 1627776000n
      },
      updatedAt: {
        matcher: "between",
        timestamps: {
          start: 1627770000n,
          end: 1627900000n
        }
      }
    },
    paginate: {
      startAfter: "doc_10",
      limit: 5
    },
    order: {
      desc: true,
      field: "updated_at"
    },
    owner: "some_owner_id_or_principal"
  }
});

The function returns the assets and various information, in the form of an object whose interface is given below.

{
  items: []; // The data - array of assets
  items_length: bigint; // The number of assets - basically items.length
  items_page?: bigint; // If the query is paginated, at what page (starting from 0) do the items find the place
  matches_length: bigint; // The total number of matching results
  matches_pages?: bigint; // If the query is paginated, the total number (starting from 0) of pages
}

Count assets

The countAssets function is used to count the number of assets in a specified collection without retrieving the actual assets.

import { countAssets } from "@junobuild/core";

const assetCount = await countAssets({
  collection: "my_collection_key"
});

Usage

This function accepts similar parameters as the listAssets function, including collection, matcher, and owner, and returns the count of matching documents.

For detailed information on how to use these parameters, refer to the List assets section.

The return value is the same as the items_length property from the listAssets function, providing the count of assets that match the criteria.

Delete

There are multiple ways to delete assets from your Storage.

Delete asset

To delete an asset, you only need to provide its fullPath. Unlike the datastore, there is no timestamp validation performed when deleting an asset.

import { deleteAsset } from "@junobuild/core";

await deleteAsset({
  collection: "images",
  storageFile: myAsset
});

Delete multiple assets

To delete multiple assets in an atomic manner, you can use the function deleteManyAssets:

import { deleteManyAssets } from "@junobuild/core";

const myAsset1 = {
  collection: "hello",
  fullPath: "/hello/world.jpg"
};

const myAsset2 = {
  collection: "data",
  fullPath: "/data/something.json"
};

await deleteManyAssets({ assets: [myAsset1, myAsset2] });

Delete filtered assets

The deleteFilteredAssets function allows you to delete multiple assets from a collection based on specific filter criteria. This function simplifies bulk deletions by leveraging the same parameters as the listAssets function for filtering.

import { deleteFilteredAssets } from "@junobuild/core";

await deleteFilteredAssets({
  collection: "my_collection_key",
  filter: {
    // Same options as filter of listAssets
  }
});

Upload asset​

Protected asset​

List assets​

Parameters​

Count assets​

Usage​

Delete​

Delete asset​

Delete multiple assets​

Delete filtered assets​

Upload asset

Protected asset

List assets

Parameters

Count assets

Usage

Delete

Delete asset

Delete multiple assets

Delete filtered assets