const getTodos = (callback) => { // FUNCTION TO MAKE REQUEST 
    const request = new XMLHttpRequest();

    request.addEventListener('readystatechange', () =>{
       if(request.readyState === 4 && request.status === 200){
           callback(undefined, request.responseText)
       }else if(request.readyState === 4){
           callback('could not fetch data', undefined)
       }
    });
    
    request.open('GET', 'https://jsonplaceholder.typicode.com/todos');
    request.send();
}

getTodos((err, data) => { // REUSABLE FUNCTION TO CHECK DATA
    console.log('callback')
    if(err){
        console.log(err)
    }else{
        console.log(data)
    }
})