var readChunk = require('read-chunk'); // npm install read-chunk
var isEot = require('is-eot');
var buffer = readChunk.sync('font.eot', 0, 36);

isEot(buffer);
//=> true

var xhr = new XMLHttpRequest();
xhr.open('GET', 'font.eot');
xhr.responseType = 'arraybuffer';

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

xhr.send();