function MyObject(val) {
	this.val = val;
	this.myCallback = this.myCallback.bind(this); // or lodash.bindall(this, 'myCallback');
}

MyObject.prototype.myCallback = function(err, data){
	console.log(err,data);
	console.log(this.val);
};

function methodThatTakesSomeTime(callback){
	// some time later...
	for(var i = 1; i<100000; i++){
		//simulate long
	}
	var err='knall';
	var data = Math.random();
	callback(err, data);
}

var testObj = 0;
for(var i = 1; i<10; i++){
	testObj = new MyObject(i);
	methodThatTakesSomeTime(testObj.myCallback) // don't be fuckin Ru***ki, use Promise and .then()
}