Check if variable holds File or Blob

Question

Javascript has both File and Blob for file representation, and both are almost the same thing. Is there a way to check if a variable is holding a File or a Blob type of data?

Answer 1

Easiest way:

a = new File([1,2,3], "file.txt"); b = new Blob([1,2,3]); c = "something else entirely";  a instanceof File > true b instanceof File > false c instanceof File > false 

Answer 2

W3.org:

'A File object is a Blob object with a name attribute, which is a string;'

In case of File:

var d = new Date(2013, 12, 5, 16, 23, 45, 600); var generatedFile = new File(["Rough Draft ...."], "Draft1.txt", {type: 'text/plain', lastModified: d});  console.log(typeof generatedFile.name == 'string'); // true 

In case of Blob:

var blob = new Blob(); console.log(typeof blob.name); // undefined 

Condition:

var isFile = typeof FileOrBlob.name == 'string';