JavaScript File : Blob

constructor

File is a Blob that represents a file from the filesystem. You can get Files from the HTMLInputElement.files property or the DataTransferItem.getAsFile() method. Use FileReader to read the contents of a File.

Spec

Constructors

new File(fileParts : Array, name : String, [filePropertyBag : Object]) : File

filePropertyBag : {

type	String	A valid mime type such as `'text/plain'`
endings	String	Must be either `'transparent'` or `'native'`

}

Creates a new File. The elements of fileParts must be of the types ArrayBuffer, ArrayBufferView, Blob, or String. If ending is set to 'native', the line endings in the file will be converted to the system line endings, such as '\r\n' for Windows or '\n' for Mac.

Example:

var file = new File(['foo', 'bar'], 'foobar.txt');

console.log('size=' + file.size);
console.log('type=' + file.type);
console.log('name=' + file.name);

var testEndings = function(string, endings) {
  var file = new File([string], { type: 'plain/text',
                                  endings: endings });
  var reader = new FileReader();
  reader.onload = function(event){
    console.log(endings + ' of ' + JSON.stringify(string) + 
                ' => ' + JSON.stringify(reader.result));
  };
  reader.readAsText(file);
};

testEndings('foo\nbar',   'native');
testEndings('foo\r\nbar', 'native');
testEndings('foo\nbar',   'transparent');
testEndings('foo\r\nbar', 'transparent');

Run

Results:

Instance Properties

lastModifiedDate : Date readonly

The last time the file was modified.

Example:

<input type='file' onchange='openFile(event)'>
<script>
  var openFile = function(event) {
    var input = event.target;

    var file = input.files[0];
    console.log(file.lastModifiedDate);
  };
</script>

Run

Results:

name : String readonly

The name of the file.

Example:

<input type='file' onchange='onFilePicked(event)'>
<script>
  var onFilePicked = function(event) {
    var input = event.target;

    var file = input.files[0];
    console.log(file.name);
  };
</script>

Run

Results:

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