Appending Blob data

Question

Is there a function for appending blob data in JavaScript I currently use the following approach:

var bb = new Blob(["Hello world, 2"], { type: "text/plain" }); bb = new Blob([bb, ",another data"], { type: "text/plain" }); 

And BlobBuilder function is not available in Chrome.

Answer 1

Blobs are "immutable" so you can't change one after making it. Constructing a new Blob that appends the data to an existing blob (as you wrote in your initial question) is a good solution.

If you don't need to use the Blob each time you append a part, you can just track an array of parts. Then you can continually append to the array and then construct the Blob at the end when you need it.

var MyBlobBuilder = function() {   this.parts = []; }  MyBlobBuilder.prototype.append = function(part) {   this.parts.push(part);   this.blob = undefined; // Invalidate the blob };  MyBlobBuilder.prototype.getBlob = function() {   if (!this.blob) {     this.blob = new Blob(this.parts, { type: "text/plain" });   }   return this.blob; };  var myBlobBuilder = new MyBlobBuilder();  myBlobBuilder.append("Hello world, 2");  // Other stuff ...   myBlobBuilder.append(",another data"); var bb = myBlobBuilder.getBlob();