Detects if a file is binary in Node.js using ✨promises✨. Similar to Perl's -B switch, in that:

• it reads the first few thousand bytes of a file
• checks for a null byte; if it's found, it's binary
• flags non-ASCII characters. After a certain number of "weird" characters, the file is flagged as binary

Much of the logic is pretty much ported from ag.

Note: if the file doesn't exist or is a directory, an error is thrown.

npm install isbinaryfile

Returns Promise<boolean> (or just boolean for *Sync). true if the file is binary, false otherwise.

• filepath - a string indicating the path to the file.

• bytes - a Buffer of the file's contents.
• size - an optional number indicating the file size.

• filepath - a string indicating the path to the file.

• bytes - a Buffer of the file's contents.
• size - an optional number indicating the file size.

Here's an arbitrary usage:

const isBinaryFile = require("isbinaryfile").isBinaryFile;
const fs = require("fs");
const filename = "fixtures/pdf.pdf";
const data = fs.readFileSync(filename);
const stat = fs.lstatSync(filename);
isBinaryFile(data, stat.size).then((result) => {
  if (result) {
    console.log("It is binary!")
  }
  else {
    console.log("No it is not.")
  }
});
const isBinaryFileSync = require("isbinaryfile").isBinaryFileSync;
const bytes = fs.readFileSync(filename);
const size = fs.lstatSync(filename).size;
console.log(isBinaryFileSync(bytes, size)); // true or false

Run npm install, then run npm test.