FileReader.result - Web APIs 编辑

The FileReader result property returns the file's contents. This property is only valid after the read operation is complete, and the format of the data depends on which of the methods was used to initiate the read operation.

Syntax

var file = instanceOfFileReader.result

Value

An appropiate string or ArrayBuffer based on which of the reading methods was used to initiate the read operation. The value is null if the reading is not yet complete or was unsuccessful.

The result types are described below.

Example

This example presents a function, read(), which reads a file from a file input. It works by creating a FileReader object and creating a listener for load events such that when then file is read, the result is obtained and passed to the callback function provided to read().

The content is handled as raw text data.

var fileInput = document.querySelector('input[type="file"]');

function read(callback) {
  var file = fileInput.files.item(0);
  var reader = new FileReader();

  reader.onload = function() {
    callback(reader.result);
  }

  reader.readAsText(file);
}

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• FileReader