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 appropriate 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.
Method | Description |
---|---|
readAsArrayBuffer() |
The result is a JavaScript ArrayBuffer containing binary data. |
readAsBinaryString() |
The result contains the raw binary data from the file in a string.
|
readAsDataURL() |
The result is a string with a data: URL representing
the file's data. |
readAsText() |
The result is text in a string. |
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
Specification | Status | Comment |
---|---|---|
File API The definition of 'result' in that specification. |
Working Draft | Initial definition |
Browser compatibility
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