为FileReader.readAsDataURL添加本地路径

Question

如何为图像添加本地路径。我试过这个

var file = new File("c:/documents and settings/downloads/image.jpg");
var reader  = new FileReader();

reader.onloadend = function () {
console.log(reader.result);
}
reader.readAsDataURL(file);

发出NS错误。