How come this `e.currentTarget` is null in debouncing function?

Question

I made a debounce function in Vanilla JS to understand how debouncing function works.

<!-- index.html -->
<div>
  <input id="text" type="text" />
</div>

// index.js
const textLog = (e) => {
  console.log('--textLog start--');
  console.log(e.target);
  console.log(e.currentTarget); // 1. e.currentTarget is null at this point
  console.log('--textLog end--');
};

const debounce = (func, wait) => {
  let timeOutId;
  return (arg) => {
    console.log('target', arg.target);
    console.log('currentTarget', arg.currentTarget); // 2. arg.currentTarget exists at this point
    if (timeOutId) {
      clearTimeout(timeOutId);
    }

    timeOutId = setTimeout(() => {
      func.call(null, arg);
    }, wait);
  };
};

const debounceLogging = debounce(textLog, 1000);
const input = document.getElementById('text');
input.addEventListener('input', debounceLogging);

This is just logging the enterd value of the input after user stopped typing for a second (1000 ms).

StackBlitz: https://stackblitz.com/edit/js-mcneev?file=index.js

In textLog(), I initially used e.currentTarget.value to get the enterd value to the input, but it threw an error saying Cannot read properties of null (reading 'value'). Then I replaced currentTarget with target and it worked as I intended.

What I know about a difference between target and currentTarget is the element that is reffereing. However, to me, this error happend because of other cause.

• I checked inside the function returned from debounce(), e.target and e.currentTarget both have values inside of them.
• But inside the textLog() called inside of the returned function, e.target is not null, but e.currentTarget is null.

Could anyone tell me what caused thie error or why this error happend? Thank you