javascript - 无法理解这段 javascript 代码如何控制流程？

Question

这是我无法理解其流程的代码，也无法理解即使在 for 循环结束后 i 的值如何仍然存在。

var printNumTwo;

for (let i = 0; i < 5; i++) {
  if (i === 2) {
    console.log("now");
    
    printNumTwo = function() {
      console.log("inside");
      return i;
    };
    
    console.log(i);
  }
  console.log(i);
}

console.log(printNumTwo());

程序的输出是

0
1
now
2
2
3
4
inside
2

Answer 1

reason of this behavior is Closures

A closure gives you access to an outer function’s scope from an inner function. In JavaScript, closures are created every time a function is created, at function creation time. mozilla doc

var printNumTwo;

for (let i = 0; i < 5; i++) {
  if (i === 2) {
    console.log("now");
    
    printNumTwo = function() {
      console.log("inside");
      return i;
    };
    
    console.log(i);
  }
  console.log(i);
}

console.log('now calling printNumTwo()')
let s=printNumTwo();

console.log('now printing return value of printNumTwo()')

console.log('retrun value of PrintNumTwo is:'+s);