揭秘 JS 中的闭包

const securebooking = function(){  let passengercount = 0;  return function(){    passengercount++;    console.log(`${passengercount} passengers`);  }}const booker = securebooking();booker();booker();booker();

let f;const g = function(){  const a = 23;  f = function() {    console.log(a*2); // 46  };};const h = function(){  const b = 777;  f = function(){    console.log(b*2); // 1554  };};g();f();console.dir(f);// f fn is reassigned using h fn. hence, old closure value i.e 'a' will be replaced with new value 'b' which can be verified using console.dir().h();f();console.dir(f);

// Boarding Passengers using Closuresconst boardPassengers = function(n, wait){  const perGroup = n / 3;  setTimeout(function(){    console.log(`We are now boarding all ${n} passengers`);    console.log(`There are 3 groups, each with ${perGroup} passengers`)  }, wait*1000);  console.log(`Will start boarding in ${wait} seconds`);}boardPassengers(180, 3);