ReactJS, onChange event on input, how to detect 'Backspace' button is currently pressed and return to previous input?

Question

Python

There are 4 inputs with a maximum length of 2.
When we enter values ​​into inputs, then remove, and the condition (e.target,value < 1), jump to the forward input with el.previousElementSibling.focus()
Condition:
const regExpValidationInputOnlyNumber = /^[0-9\b]+$/;
if (!event.target.value.length && event.target.value === regExpValidationInputBackspace.test(event.target.value)) {
event.target.previousElementSibling.focus();
console log('true');
}
Please tell me what I'm writing wrong. Thank you!

Answer 1

https://kivy.org/doc/stable/api-kivy.uix.button.html

Answer 2

in response to the header - no,
because first, before using kiwi, you need to understand how python itself works. it's like driving a car and not having a license

Answer 3

The code you provided will focus the previous input if the current input is empty and validated (wtf?). You need to attach two handlers to inputs: input and keydown. In the keydown handler, you look at which key was pressed and, if backspace was pressed, set a boolean to tell you to jump to the previous input if the current input becomes empty.
Example