javascript var scope question in for loop

Question

What will the console log output be, when the corresponding the button of 'button 5' is clicked?

The answer is clicked button 10 but not clicked button 5 , why??

Please help me solve the problem

for (var i = 0; i < 10; i++) {
  let button = document.createElement("button");
  button.textContent = "button " + i;
  button.onclick = function() {
    console.log("clicked button " + i);
  };
  document.body.append(button);
}