Question

http://javascriptissexy.com/understand-javascript-closures-with-ease/的最后一个例子是：

function celebrityIDCreator (theCelebrities) {
    var i;
    var uniqueID = 100;
    for (i = 0; i < theCelebrities.length; i++) {
        theCelebrities[i]["id"] = function (j)  { // the j parametric variable is the i passed in on invocation of this IIFE
            return function () {
                return uniqueID + j; // each iteration of the for loop passes the current value of i into this IIFE and it saves the correct value to the array
            } () // BY adding () at the end of this function, we are executing it immediately and returning just the value of uniqueID + j, instead of returning a function.
        } (i); // immediately invoke the function passing the i variable as a parameter
    }
    return theCelebrities;
};

var actionCelebs = [{name:"Stallone", id:0}, {name:"Cruise", id:0}, {name:"Willis", id:0}];

var createIdForActionCelebs = celebrityIDCreator (actionCelebs);

var stalloneID = createIdForActionCelebs[0];

console.log(stalloneID.id); // 100

console.log(createIdForActionCelebs[1].id); // 101

我不明白为什么这里需要IIFE，我用celebrityIDCreator替换了var celebrityIDCreator = function(theCelebrities) { var i; var uniqueID = 100; for (i = 0; i < theCelebrities.length; i++) { theCelebrities[i]["id"] = function (j) { return uniqueID + j; // return function () { // } () ; } (i); } return theCelebrities; };并产生了相同的结果：

public function init()
{
    parent::init();

    $this->on(self::EVENT_AFTER_INSERT, [$this, 'exampleMethodHere']);
}

有人可以解释这个吗？我错过了什么吗？

Answer 1

我认为这是博客上的一个错误。如果您看到 Closures Gone Awry 部分的第一个示例，则id将作为函数创建。但是，在你所指的第二个例子中，它旨在解决第一个中的错误，id被创建为一个属性。

我认为第二个例子应该是这样的，以使其与第一个类似。请注意代码中的注释，在IIFE附近以及id作为函数的消耗

function celebrityIDCreator(theCelebrities) {
  var i;
  var uniqueID = 100;
  for (i = 0; i < theCelebrities.length; i++) {
    theCelebrities[i]["id"] = function(j) { // the j parametric variable is the i passed in on invocation of this IIFE
      return function() {
        return uniqueID + j; // each iteration of the for loop passes the current value of i into this IIFE and it saves the correct value to the array
      } // NOTE. Not an IIFE
    }(i); // immediately invoke the function passing the i variable as a parameter
  }
  return theCelebrities;
};


var actionCelebs = [{
  name: "Stallone",
  id: 0
}, {
  name: "Cruise",
  id: 0
}, {
  name: "Willis",
  id: 0
}];


var createIdForActionCelebs = celebrityIDCreator(actionCelebs);


var stalloneID = createIdForActionCelebs[0];

console.log(stalloneID.id()); // 100 NOTE: Use as function

console.log(createIdForActionCelebs[1].id()); // 101 NOTE: Use as function

除此之外，我相信你不会错过任何东西。如果id需要属性，那么您的代码是正确的。

从轻松理解JavaScript闭包中了解示例

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