Problem understanding callback hell in JavaScript

function task1(callback) {
    setTimeout(function() {
        console.log("Task 1 complete");
        callback();  // calling task2 when task1 finishes
    }, 1000);  // 1-second delay
}

function task2(callback) {
    setTimeout(function() {
        console.log("Task 2 complete");
        callback();  // calling task3 when task2 finishes
    }, 1000);  // 1-second delay
}

function task3(callback) {
    setTimeout(function() {
        console.log("Task 3 complete");
        callback();  // calling task4 when task3 finishes
    }, 1000);  // 1-second delay
}

function task4() {
    setTimeout(function() {
        console.log("Task 4 complete");
    }, 1000);  // 1-second delay
}

// Execute the tasks in sequence
task1(function() {
    task2(function() {
        task3(function() {
            task4();  // no more callbacks needed
        });
    });
});

// Execute the tasks in sequence
task1(function() {
    task2(function() {
        task3(function() {
            task4();  // no more callbacks needed
        });
    });
});