JSFiddle - React, Tailwind, and code Playground

JavaScript

const intervalFn = (mount) => {
	const closedVariable = 0;
	if (mount)
    setInterval(() => {
      setClosedVariable(closedVariable + 1)
    }, 1000)
}

function setClosedVariable(num) {
	closedVariable = num;
  console.log(closedVariable);
  intervalFn(false);
}

intervalFn(true);

// prints incremented closed variable as expected
// closedVariable is correctly updated