JavaScript

Scope

const outerFunc = () => {
  let outerNum = 1;

  const innerFunc = () => {
    console.log("Printing outerNum in innerFunc: " + outerNum);
    outerNum = 4;
  }
  innerFunc();

  console.log("Printing outerNum in outerFunc: " + outerNum);
}

outerFunc();

const outerFunc = () => {

  const innerFunc = () => {
    const innerNum = 2;
    console.log("Printing innerNum in innerFunc: " + innerNum);
  }
  innerFunc();

  console.log("Printing innerNum in outerFunc: " + innerNum); // ReferenceError
}

outerFunc();