FileReader objects can read from a file or a blob, in one of three formats: String (readAsText). 第01引数 ... 解釈してテキスト文字列を得る） // -----file_reader. It exposes those 4 reading methods we can use to start a reading process: readAsText() readAsDataURL() readAsArrayBuffer() readAsBinaryString() and an abort() method to halt any reading operation.
For that reason, you can't just refer to the file contents after calling it. FileReader.readAsDataURL() Starts reading the contents of the specified Blob, once finished, the result attribute contains a data: URL representing the file's data. It not only lightens the load of web server but also saves the time of uploading files. JSFiddle or its authors are not responsible or liable for any loss or damage of any kind during the usage of provided code. It is very easy to use FileReader.readAsText() to process a 300K log file. Links. readAsText(file, encoding)readAsDataURL(file)readAsBinaryString(file)readAsArrayBuffer(file)Pass in a File or Blob …
new FileReader : FileReader.
However, when the file size grows to 1GB, or even 2GB, then the page might crash in browser or not function correctly. FileReader is used to read the contents of a Blob or File.
The FileReader API in HTML5 allows web browsers to access user files without uploading the files to the web servers. answer 1 >> 解决方法. - FileReader.readAsText(Blob|File, opt_encoding) – The result property will contain the file/blob’s data as a text string. The FileReader object asynchronously reads the content of a file. Constructors. There's a whole bunch of different methods available that allow you to get a file's content in various formats. We usually get File objects from user input, like or Drag’n’Drop events (ondragend). The readAsText() method used above is asynchronous. In this tutorial, I am going to share with you how you can use HTML5 FileReader API to upload images and text files from the client side in the web browser. FileReader.readAsText() Starts reading the contents of the specified Blob, once finished, the result attribute contains the contents of the file as a text string. Spec.
HTML5 FileReader API provides a convenient way to communicate with local files through the local device. ... readAsText (blob : Blob, [encoding : String]) : undefined. Bug tracker Roadmap (vote for features) About Docs Service status.
To set File content into innerHtml you must first read the file.loadend event fires only when file is fully readed, and you can access its contect without errors:.
FileReaderオブジェクトには、下記のようなメソッドがあり（非推奨のものは除く）、Blobオブジェクトを様々な形式で読み取ることができる readAsArrayBuffer() →ArrayBuffer; readAsDataURL() →DataURL; readAsText() →文字列; abort() →読み取り中断 Use the optional encoding parameter can specify a different format. By default the string is decoded as ‘ UTF-8’. In addition to Blob methods and properties, File objects also have name and lastModified properties, plus the internal ability to read from filesystem. The FileReader API is really handy if you need to read a file using JavaScript. Every byte is represented by an integer in the range [0..255].
Like the also asynchronous Ajax calls, the FileReader also has loading states that help to ascertain the progress of the read. Begins reading from blob as a string. The result will be stored on this.result after the 'load' event fires. HTML5 FileReader API allows you to upload files or blob in the browser very easily. FileReader.readAsText( Blob , "文字セット" ) :Void.