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Blob

Namespace: SpawnDev.SpawnJS.JSObjects
Inherits: SpawnJSObject
Source: JSObjects/Blob.cs
MDN Reference: Blob on MDN

The Blob object represents a blob, which is a file-like object of immutable, raw data; they can be read as text or binary data, or converted into a ReadableStream so its methods can be used for processing the data. https://developer.mozilla.org/en-US/docs/Web/API/Blob

Constructors

Signature Description
Blob(SpawnJSObjectReference _ref) Deserialization constructor
Blob() New Blob constructor
Blob(IEnumerable<ArrayBuffer> buffers, BlobOptions? options) Returns a newly created Blob object which contains a concatenation of all of the data in the array passed into the constructor.
Blob(IEnumerable<string> buffers, BlobOptions? options) Returns a newly created Blob object which contains a concatenation of all of the data in the array passed into the constructor.
Blob(IEnumerable<Blob> blobs, BlobOptions? options) Returns a newly created Blob object which contains a concatenation of all of the data in the array passed into the constructor.
Blob(IEnumerable<byte[]> blobs, BlobOptions? options) Returns a newly created Blob object which contains a concatenation of all of the data in the array passed into the constructor.
Blob(IEnumerable<TypedArray> typedArrays, BlobOptions? options) Returns a newly created Blob object which contains a concatenation of all of the data in the array passed into the constructor.
Blob(IEnumerable<DataView> dataViews, BlobOptions? options) Returns a newly created Blob object which contains a concatenation of all of the data in the array passed into the constructor.
Blob(IEnumerable<Union<ArrayBuffer, TypedArray, DataView, Blob, string>> data, BlobOptions? options) Returns a newly created Blob object which contains a concatenation of all of the data in the array passed into the constructor.

Properties

Property Type Access Description
Size long get The size, in bytes, of the data contained in the Blob object.
Type string get A string indicating the MIME type of the data contained in the Blob. If the type is unknown, this string is empty.

Methods

Method Return Type Description
Text() Task<string> Returns a promise that resolves with a string containing the entire contents of the Blob interpreted as UTF-8 text.
ArrayBuffer() Task<ArrayBuffer> Returns a promise that resolves with an ArrayBuffer containing the entire contents of the Blob as binary data.
Slice(long startPos, long endPos, string contentType) Blob The Blob interface's slice() method creates and returns a new Blob object which contains data from a subset of the blob on which it's called. An index into the Blob indicating the first byte to include in the new Blob. If you specify a negative value, it's treated as an offset from the end of the Blob toward the beginning. For example, -10 would be the 10th from last byte in the Blob. The default value is 0. If you specify a value for start that is larger than the size of the source Blob, the returned Blob has size 0 and contains no data. An index into the Blob indicating the first byte that will not be included in the new Blob (i.e. the byte exactly at this index is not included). If you specify a negative value, it's treated as an offset from the end of the Blob toward the beginning. For example, -10 would be the 10th from last byte in the Blob. The default value is size. The content type to assign to the new Blob; this will be the value of its type property. The default value is an empty string.
Slice(long startPos, long endPos) Blob The Blob interface's slice() method creates and returns a new Blob object which contains data from a subset of the blob on which it's called. An index into the Blob indicating the first byte to include in the new Blob. If you specify a negative value, it's treated as an offset from the end of the Blob toward the beginning. For example, -10 would be the 10th from last byte in the Blob. The default value is 0. If you specify a value for start that is larger than the size of the source Blob, the returned Blob has size 0 and contains no data. An index into the Blob indicating the first byte that will not be included in the new Blob (i.e. the byte exactly at this index is not included). If you specify a negative value, it's treated as an offset from the end of the Blob toward the beginning. For example, -10 would be the 10th from last byte in the Blob. The default value is size.
Slice(long startPos) Blob The Blob interface's slice() method creates and returns a new Blob object which contains data from a subset of the blob on which it's called. An index into the Blob indicating the first byte to include in the new Blob. If you specify a negative value, it's treated as an offset from the end of the Blob toward the beginning. For example, -10 would be the 10th from last byte in the Blob. The default value is 0. If you specify a value for start that is larger than the size of the source Blob, the returned Blob has size 0 and contains no data.
Stream() ReadableStream Returns a ReadableStream that can be used to read the contents of the Blob.
FromDataURL(string dataUrl) Blob Creates a new Blob from a data url
ToObjectURL() string Returns an ObjectURL created using URL.CreateObjectURL
ToDataURLAsync() Task<string> Returns the blob as a data url string
StartDownload(string fileName) Task Start download of the blob

Example

// Create a Blob from string data with a MIME type
using var blob = new Blob(
    new[] { "{\"hello\": \"world\"}" },
    new BlobOptions { Type = "application/json" }
);

// Check size and type
Console.WriteLine($"Size: {blob.Size} bytes");
Console.WriteLine($"Type: {blob.Type}");

// Read the Blob content as text
var text = await blob.Text();
Console.WriteLine($"Content: {text}");

// Read the Blob content as an ArrayBuffer
using var buffer = await blob.ArrayBuffer();
byte[] bytes = buffer.ReadBytes();

// Create a Blob from binary data
using var binaryBlob = new Blob(
    new[] { new byte[] { 0x48, 0x65, 0x6C, 0x6C, 0x6F } },
    new BlobOptions { Type = "application/octet-stream" }
);

// Slice a portion of the Blob
using var sliced = blob.Slice(0, 5, "text/plain");

// Get a ReadableStream from the Blob
using var stream = blob.Stream();

// Create an object URL for use in links or images
var objectUrl = blob.ToObjectURL();
// ... use the URL ...
URL.RevokeObjectURL(objectUrl);

// Convert to a data URL (base64)
var dataUrl = await blob.ToDataURLAsync();

// Trigger a file download from the Blob
await blob.StartDownload("data.json");