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author | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:41:45 -0500 |
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committer | Peter Bengtsson <mail@peterbe.com> | 2020-12-08 14:41:45 -0500 |
commit | 1109132f09d75da9a28b649c7677bb6ce07c40c0 (patch) | |
tree | 0dd8b084480983cf9f9680e8aedb92782a921b13 /files/fa/web/api/blob/index.html | |
parent | 4b1a9203c547c019fc5398082ae19a3f3d4c3efe (diff) | |
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diff --git a/files/fa/web/api/blob/index.html b/files/fa/web/api/blob/index.html new file mode 100644 index 0000000000..e2de156275 --- /dev/null +++ b/files/fa/web/api/blob/index.html @@ -0,0 +1,129 @@ +--- +title: Blob +slug: Web/API/Blob +tags: + - API + - Files + - NeedsMobileBrowserCompatibility + - NeedsTranslation + - Reference + - TopicStub + - WebAPI +translation_of: Web/API/Blob +--- +<div>{{APIRef("File API")}}</div> + +<p>A <code>Blob</code> object represents a file-like object of immutable, raw data. Blobs represent data that isn't necessarily in a JavaScript-native format. The {{domxref("File")}} interface is based on <code>Blob</code>, inheriting blob functionality and expanding it to support files on the user's system.</p> + +<p>To construct a <code>Blob</code> from other non-blob objects and data, use the {{domxref("Blob.Blob", "Blob()")}} constructor. To create a blob that contains a subset of another blob's data, use the {{domxref("Blob.slice()", "slice()")}} method. To obtain a <code>Blob</code> object for a file on the user's file system, see the {{domxref("File")}} documentation.</p> + +<p>The APIs accepting <code>Blob</code> objects are also listed on the {{domxref("File")}} documentation.</p> + +<div class="note"> +<p><strong>Note:</strong> The <code>slice()</code> method had initially taken <code>length</code> as the second argument to indicate the number of bytes to copy into the new <code>Blob</code>. If you specified values such that <code>start + length</code> exceeded the size of the source <code>Blob</code>, the returned <code>Blob</code> contained data from the start index to the end of the source <code>Blob</code>.</p> +</div> + +<div class="note"><strong>Note:</strong> Be aware that the <code>slice()</code> method has vendor prefixes on some browsers and versions: <code>blob.mozSlice()</code> for Firefox 12 and earlier and <code>blob.webkitSlice()</code> in Safari. An old version of the <code>slice()</code> method, without vendor prefixes, had different semantics, and is obsolete. The support for <code>blob.mozSlice()</code> has been dropped with Firefox 30.</div> + +<h2 id="Constructor">Constructor</h2> + +<dl> + <dt>{{domxref("Blob.Blob", "Blob(blobParts[, options])")}}</dt> + <dd>Returns a newly created <code>Blob</code> object whose content consists of the concatenation of the array of values given in parameter.</dd> +</dl> + +<h2 id="Properties">Properties</h2> + +<dl> + <dt>{{domxref("Blob.size")}} {{readonlyinline}}</dt> + <dd>The size, in bytes, of the data contained in the <code>Blob</code> object.</dd> + <dt>{{domxref("Blob.type")}} {{readonlyinline}}</dt> + <dd>A string indicating the MIME type of the data contained in the <code>Blob</code>. If the type is unknown, this string is empty.</dd> +</dl> + +<h2 id="Methods">Methods</h2> + +<dl> + <dt>{{domxref("Blob.slice()", "Blob.slice([start[, end[, contentType]]])")}}</dt> + <dd>Returns a new <code>Blob</code> object containing the data in the specified range of bytes of the source <code>Blob</code>.</dd> +</dl> + +<h2 id="Examples">Examples</h2> + +<h3 id="Blob_constructor_example_usage">Blob constructor example usage</h3> + +<p>The {{domxref("Blob.Blob", "Blob() constructor")}} allows one to create blobs from other objects. For example, to construct a blob from string:</p> + +<pre class="brush: js">var debug = {hello: "world"}; +var blob = new Blob([JSON.stringify(debug, null, 2)], {type : 'application/json'});</pre> + +<div class="warning"> +<p>Before the Blob constructor was available, this could be accomplished through the {{domxref("BlobBuilder")}} API, which is now deprecated:</p> + +<pre class="brush: js">var builder = new BlobBuilder(); +var fileParts = ['<a id="a"><b id="b">hey!</b></a>']; +builder.append(fileParts[0]); +var myBlob = builder.getBlob('text/xml'); +</pre> +</div> + +<h3 id="Example_for_creating_a_URL_to_a_typed_array_using_a_blob">Example for creating a URL to a typed array using a blob</h3> + +<p>The following code:</p> + +<pre class="brush: js">var typedArray = GetTheTypedArraySomehow(); +var blob = new Blob([typedArray.buffer], {type: 'application/octet-stream'}); // pass a useful mime type here +var url = URL.createObjectURL(blob); +// url will be something like: blob:d3958f5c-0777-0845-9dcf-2cb28783acaf +// now you can use the url in any context that regular URLs can be used in, for example img.src, etc. +</pre> + +<h3 id="Example_for_extracting_data_from_a_Blob">Example for extracting data from a Blob</h3> + +<p>One way to read content from a Blob is to use a {{domxref("FileReader")}}. The following code reads the content of a Blob as a typed array:</p> + +<pre class="brush: js">var reader = new FileReader(); +reader.addEventListener("loadend", function() { + // reader.result contains the contents of blob as a typed array +}); +reader.readAsArrayBuffer(blob);</pre> + +<p>Another way to read content from a Blob is to use a Response. The following code reads the content of a Blob as text:</p> + +<pre class="brush: js">var text = await (new Response(blob)).text(); +</pre> + +<p>By using other methods of {{domxref("FileReader")}}, it is possible to read the contents of a Blob as a string or a data URL.</p> + +<h2 id="Specifications">Specifications</h2> + +<table class="standard-table"> + <tbody> + <tr> + <th scope="col">Specification</th> + <th scope="col">Status</th> + <th scope="col">Comment</th> + </tr> + <tr> + <td>{{SpecName('File API','#blob','Blob')}}</td> + <td>{{Spec2('File API')}}</td> + <td>Initial definition</td> + </tr> + </tbody> +</table> + +<h2 id="Browser_compatibility">Browser compatibility</h2> + + + +<p>{{Compat("api.Blob")}}</p> + +<h2 id="See_also">See also</h2> + +<ul> + <li>{{domxref("BlobBuilder")}}</li> + <li>{{domxref("FileReader")}}</li> + <li>{{domxref("File")}}</li> + <li>{{domxref("URL.createObjectURL")}}</li> + <li><a href="/en-US/docs/Components.utils.importGlobalProperties">Components.utils.importGlobalProperties</a></li> +</ul> |