![]() ![]() ![]() window.Enabling RuneScape Access in Mac OS X 10.6 and 10.7 This will be fired whenever the user selects a file. We also setup an event listener on the fileInput that listens for the change event. Here we get references to the file and the element and store them in variables called fileInput and fileDisplayArea. Create a new file called text.js to house this code.įirst we need to get references to the important elements within our HTML. Now it’s time to start writing the JavaScript code for your application. You can find a copy of the stylesheet used in this demo in the code resources. We also need to add a element that will be used for displaying the file’s contents. We are going to use a file to handle selecting our file but you could also use drag and drop. To get started we first need to setup the HTML for our demo. In this section you are going to learn how to build a small JavaScript application that reads a text file and displays it’s contents within a element. See the Demo Download The Code View on CodePen Reading Text Files With The FileReader API Example: Reading Text Files With The FileReader API Now that you have an understanding of how the FileReader API works lets take a look at a couple of examples. This can come in handy when reading large files. The abort() method will stop a read operation. They can come in handy when manipulating files (like converting a JPEG image to PNG). An ArrayBuffer is a fixed-length binary data buffer. The readAsArrayBuffer() method will read a Blob or File object and produce an ArrayBuffer. Reader.readAsBinaryString(file) readAsArrayBuffer() If you use readAsBinaryString() along with the ndAsBinary() method you can upload any file to a server using JavaScript. The method returns the raw binary data from the file. ![]() The readAsBinaryString() method can be used to read any type of file. Reader.readAsDataURL(file) readAsBinaryString() We will look at how to do this later in the images demo. You can use this data URL for things like setting the src property for an image. This is basically a base64 encoded string of the file data. The readAsDataURL() method takes in a File or Blob and produces a data URL. Reader.readAsText(file, encoding) readAsDataURL() You will need to use this same approach for all of the read methods provided by FileReader. When the onload event is called we can examine the result property of our FileReader instance to get the file’s contents. If you don’t specify an encoding UTF-8 is assumed by default.Īs this is an asynchronous method we need to setup an event listener for when the file has finished loading. The second parameter is used to specify the encoding of the file. The first parameter is for the File or Blob object that is to be read. The readAsText() method can be used to read text files. In the following sections we are going to take a look at the methods provided by FileReader. The following code shows how to create a new instance of FileReader. This is particularly useful when dealing with large files. These methods are all asynchronous which means that your program will not stall whilst a file is being read. The FileReader interface provides a number of methods that can be used to read either File or Blob objects. The second will read an image file and then generate a data URL that will be used to display the image on the page.įree trial on Treehouse: Do you want to learn more about HTML5? Click here to try a free trial on Treehouse. The first application will handle reading and then displaying the contents of a text file. You will be creating two demo applications. In this blog post you are going to learn how to use the FileReader API to read the contents of a file from your local hard drive. These APIs make it much easier to accomplish tasks like reading and writing files or uploading a file created using JavaScript. HTML5 saw the introduction of a number of new APIs that can be used to handle files in the browser. ![]()
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