Question

如果您想在JavaScript中使用某种私有变量，可以将代码放在匿名闭包中，对吗？现在，由于包含了let，闭包的这种特定用例是否消失了？还是仍然相关？

顶级示例：

// global variable a
var a = 6;

// using let
{
  // new variable a that only lives inside this block
  let a = 5;
  console.log(a); // => 5
}

console.log(a); // => 6

// using a closure
(function() {
  // again a new variable a that only lives in this closure
  var a = 3;
  console.log(a); // => 3
})();

console.log(a); // => 6

Answer 1

在Javascript中有一个叫做Hoisting的东西，甚至在初始化之前就将其“提升”了。

// global variable a
var a = 6;

// using let
{
  // new variable a that only lives inside this block
  let a = 5;
  console.log(a); // => 5
}

console.log(a); // => 6

// using a closure
(function() {
  // again a new variable a that only lives in this closure
  var a = 3;
  console.log(a); // => 3
})();

console.log(a); // => 6

因此此代码更改为：

// The global variable 'a' is hoisted on the top of current scope which is Window as of now
var a;

// Initialization takes place as usual
a = 6;


// This is a block
{

  // This local variable 'a' is hoisted on the top of the current scope which is the 'block'
  let a;

  a = 5;
  console.log(a); // => 5
}

console.log(a); // => 6

// Using an IIFE
(function() {

  // This local variable 'a' is hoisted on the top of the current scope which is the block of IIFE
  var a;

  a = 3;
  console.log(a); // => 3
})();

console.log(a); // => 6

在ES6之前，我们曾经使用IIFEs来创建不会污染全局范围的变量，但是在ES6之后，我们通常使用let和const，因为它们提供了block-scope

让我们替换具有私有变量的匿名闭包吗？

1 个答案: