import {readChunkSync} from 'read-chunk';
import isPsd from 'is-psd';

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

isPsd(buffer);
//=> true

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

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

xhr.send();