import {readChunkSync} from 'read-chunk';
import isTif from 'is-tif';

const buffer = readChunkSync('unicorn.tif', {length: 4});

isTif(buffer);
//=> true

const xhr = new XMLHttpRequest();
xhr.open('GET', 'unicorn.tif');
xhr.responseType = 'arraybuffer';

xhr.onload = () => {
	isTif(new Uint8Array(this.response));
	//=> true
};

xhr.send();