construct Blob with sliced buffer

Author: tinovyatkin

index.js

@@ -11,18 +11,22 @@ const wm = new WeakMap();
 
 class Blob {
 	/**
-	 * The Blob() constructor returns a new Blob object. The content of the blob consists of the concatenation of the values given in the parameter array.
-	 * @param {(ArrayBufferLike | ArrayBufferView | Blob | Buffer | string)[]} blobParts
-	 * @param {{ type?: string }} [options]
-	 */
+   * The Blob() constructor returns a new Blob object. The content of the blob consists of the concatenation of the values given in the parameter array.
+   * @param {(ArrayBufferLike | ArrayBufferView | Blob | Buffer | string)[]} blobParts
+   * @param {{ type?: string }} [options]
+   */
 	constructor(blobParts = [], options = {type: ''}) {
 		const buffers = blobParts.map(element => {
 			if (Buffer.isBuffer(element)) {
 				return element;
 			}
 
 			if (ArrayBuffer.isView(element)) {
-				return Buffer.from(element.buffer, element.byteOffset, element.byteLength);
+				return Buffer.from(
+					element.buffer,
+					element.byteOffset,
+					element.byteLength
+				);
 			}
 
 			if (types.isAnyArrayBuffer(element)) {
@@ -33,12 +37,15 @@ class Blob {
 				return wm.get(element).buffer;
 			}
 
-			return Buffer.from(typeof element === 'string' ? element : String(element));
+			return Buffer.from(
+				typeof element === 'string' ? element : String(element)
+			);
 		});
 
 		const buffer = Buffer.concat(buffers);
 
-		const type = options.type === undefined ? '' : String(options.type).toLowerCase();
+		const type =
+      options.type === undefined ? '' : String(options.type).toLowerCase();
 
 		wm.set(this, {
 			type: /[^\u0020-\u007E]/.test(type) ? '' : type,
@@ -47,38 +54,41 @@ class Blob {
 	}
 
 	/**
-	 * The Blob interface's size property returns the size of the Blob in bytes.
-	 */
+   * The Blob interface's size property returns the size of the Blob in bytes.
+   */
 	get size() {
 		return wm.get(this).buffer.byteLength;
 	}
 
 	/**
-	 * The type property of a Blob object returns the MIME type of the file.
-	 */
+   * The type property of a Blob object returns the MIME type of the file.
+   */
 	get type() {
 		return wm.get(this).type;
 	}
 
 	/**
-	 * The text() method in the Blob interface returns a Promise that resolves with a string containing the contents of the blob, interpreted as UTF-8.
-	 */
+   * The text() method in the Blob interface returns a Promise that resolves with a string containing the contents of the blob, interpreted as UTF-8.
+   */
 	async text() {
 		return wm.get(this).buffer.toString();
 	}
 
 	/**
-	 * The arrayBuffer() method in the Blob interface returns a Promise that resolves with the contents of the blob as binary data contained in an ArrayBuffer.
-	 */
+   * The arrayBuffer() method in the Blob interface returns a Promise that resolves with the contents of the blob as binary data contained in an ArrayBuffer.
+   */
 	async arrayBuffer() {
 		const buf = wm.get(this).buffer;
-		const ab = buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength);
+		const ab = buf.buffer.slice(
+			buf.byteOffset,
+			buf.byteOffset + buf.byteLength
+		);
 		return ab;
 	}
 
 	/**
-	 * The Blob interface's stream() method returns a ReadableStream which upon reading returns the data contained within the Blob.
-	 */
+   * The Blob interface's stream() method returns a ReadableStream which upon reading returns the data contained within the Blob.
+   */
 	stream() {
 		return Readable.from(wm.get(this).buffer);
 	}
@@ -88,19 +98,19 @@ class Blob {
 	}
 
 	/**
-	 * @returns {string}
-	 */
+   * @returns {string}
+   */
 	toString() {
 		return Object.prototype.toString.call(this);
 	}
 
 	/**
-	 * 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.
-	 *
-	 * @param {number} [start]
-	 * @param {number} [end]
-	 * @param {string} [contentType]
-	 */
+   * 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.
+   *
+   * @param {number} [start]
+   * @param {number} [end]
+   * @param {string} [contentType]
+   */
 	slice(start, end, contentType) {
 		const {size} = this;
 
@@ -124,14 +134,10 @@ class Blob {
 		}
 
 		const span = Math.max(relativeEnd - relativeStart, 0);
-		const slicedBuffer = wm.get(this).buffer.slice(
-			relativeStart,
-			relativeStart + span
-		);
-		const blob = new Blob([], {type: contentType});
-		const _ = wm.get(blob);
-		_.buffer = slicedBuffer;
-		return blob;
+		const slicedBuffer = wm
+			.get(this)
+			.buffer.slice(relativeStart, relativeStart + span);
+		return new Blob([slicedBuffer], {type: contentType});
 	}
 }