Keep track of how many times a recursive function was called

Answer 1

You can use closure for this.

Just simply store counter into the closure of function.

Here is example:

function singleDigitDecorator() {
	let counter = 0;

	return function singleDigitWork(num, isCalledRecursively) {

		// Reset if called with new params 
		if (!isCalledRecursively) {
			counter = 0;
		}

		counter++; // *

		console.log(`called ${counter} times`);

		let number = [...(num + "")].map(Number).reduce((x, y) => {
			return x * y;
		});

		if (number <= 9) {
			console.log(number);
		} else {
			console.log(number);

			return singleDigitWork(number, true);
		}
	};
}

const singleDigit = singleDigitDecorator();

singleDigit(39);

console.log('`===========`');

singleDigit(44);