我正在生成一个函数并使用IIFE将其推送到数组，如下所示：
var arr = [];
var k;
for(var i=0;i<3;i++) {
k = {"val" : i};
arr.push(
(function(j) {
return function() {
console.log(j)
};
}(k))
)
}
console.log(arr[0](), arr[1](), arr[2]());
输出：
Object {val: 0}
Object {val: 1}
Object {val: 2}
但是我传递k，这是使用i生成的对象。由于对象是通过引用传递的，因此我希望它能够记录值为2,2,2的对象，但我获得了0,1,2。当通过值传递的原始类型时，这不是通常的行为吗？ ，为什么即使我使用传递引用（对象）也会发生同样的事情？
答案 0 :(得分：4)
你得到0,1,2而不是3,3,3，因为k的值被传递到函数中。 k的值是对象引用。 JavaScript没有任何形式的pass-by-reference，因此函数接收的不是对k 变量的引用，它是k中对象引用的副本。 1}}当你调用函数时。在下一个传递中，您创建一个新对象并将其放在k变量中，但这对最内层函数关闭的j变量的值完全没有影响。
将对象引用想象成一个大数组（内存）的索引，它告诉JavaScript引擎对象所在的位置。 k包含该引用（数字），而不是实际对象。将引用复制到第二个变量（或将其传递给函数）时，对象只有两个引用副本，但只有一个对象。
让我们简化，并在其上抛出一些ASCII艺术:: - ）
var k = {val: 0};
在这些代码行之后，这是我们在内存中的内容（省略了一些不必要的细节）：
+−−−−−−−−−−−−−−−−+
k:REF#123−−−−−−−−−−−>| Object@REF#123 |
+−−−−−−−−−−−−−−−−+
| val: 0 |
+−−−−−−−−−−−−−−−−+
k包含引用（我任意称之为REF#123，但我们实际上从未看到原始值）;对象在别处。
现在，如果我们这样做：
var j = k;
......我们有这个：
k:REF#123−−−−−−+
| +−−−−−−−−−−−−−−−−+
+−−−−>| Object@REF#123 |
| +−−−−−−−−−−−−−−−−+
j:REF#123−−−−−−+ | val: 0 |
+−−−−−−−−−−−−−−−−+
请注意k和j具有相同的值REF＃123。因此，无论您查看哪个变量，JavaScript引擎都将转到内存中的该对象。
现在假设我们这样做：
k = {val: 1};
现在我们有了一个新对象，它有一个不同的引用：
+−−−−−−−−−−−−−−−−+
k:REF#462−−−−−−−−−−−>| Object@REF#462 |
+−−−−−−−−−−−−−−−−+
| val: 1 |
+−−−−−−−−−−−−−−−−+
+−−−−−−−−−−−−−−−−+
j:REF#123−−−−−−−−−−−>| Object@REF#123 |
+−−−−−−−−−−−−−−−−+
| val: 0 |
+−−−−−−−−−−−−−−−−++
{val: 1}创建了一个新对象。将该对象的引用分配给k会给它一个新值（新对象的引用）。 j的值未发生变化，因为k和j没有相互关联。
将k传递给函数并将值作为j接收就像上面的j = k一样：k的值已通过进入函数，并输入参数j。回到原始代码：
var arr = [];
var k;
for(var i=0;i<3;i++) {
k = {"val" : i};
arr.push(
(function(j) {
return function() {
console.log(j)
};
}(k))
)
}
console.log(arr[0](), arr[1](), arr[2]());
...每次调用中间的IIFE都会创建一个执行上下文，并附加一个环境记录。从概念上讲，环境记录是包含变量和参数值的对象，对于函数调用是这样的（您无法在代码中访问此对象，它是规范中的概念，不一定是JavaScript引擎中的文字内容）。该环境记录包含j参数。 IIFE创建了一个新函数，它记住了对它所创建的环境的引用（使用一个名为[[Environment]]的内部插槽），并返回该函数;函数被推入数组。
所以这是第一个循环之后的内存（再次遗漏了一些不必要的细节）：
+−−−−−−−−−−−−−−+
k−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+−>| Object@REF#2 |
| +−−−−−−−−−−−−−−+
+−−−−−−−−−−+ | | val: 0 |
arr−−−>| Array | | +−−−−−−−−−−−−−−+
+−−−−−−−−−−+ +−−−−−−−−−−−−−−−−−+ |
| 0: REF#1 |−−−−>| Function@REF#1 | |
| 1: REF#3 |−−+ +−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ |
+−−−−−−−−−−+ | | [[Environment]] |−>| Environment | |
| +−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ |
| | j: REF#2 |−+
| +−−−−−−−−−−−−−+
| +−−−−−−−−−−−−−−−−−+
+−>| Function@REF#3 |
+−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+
| [[Environment]] |−>| Environment |
+−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+
| j: REF#4 |
+−−−−−−−−−−−−−+
在第二个循环之后，你有这个：
+−−−−−−−−−−−−−−+
k−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+−>| Object@REF#4 |
| +−−−−−−−−−−−−−−+
| | val: 1 |
+−−−−−−−−−−−−−−+ | +−−−−−−−−−−−−−−+
+−>| Object@REF#2 | |
| +−−−−−−−−−−−−−−+ |
| | val: 0 | |
| +−−−−−−−−−−−−−−+ |
| |
| |
+−−−−−−−−−−+ | |
arr−−−>| Array | | |
+−−−−−−−−−−+ +−−−−−−−−−−−−−−−−−+ | |
| 0: REF#1 |−−−>| Function@REF#1 | | |
| 1: REF#3 |−+ +−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ | |
+−−−−−−−−−−+ | | [[Environment]] |−−>| Environment | | |
| +−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ | |
| | j: REF#2 |−+ |
| +−−−−−−−−−−−−−+ |
| +−−−−−−−−−−−−−−−−−+ |
+−>| Function@REF#3 | |
+−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ |
| [[Environment]] |−−>| Environment | |
+−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ |
| j: REF#4 |−−−−−−−−−−−−−−−−−−−−−+
+−−−−−−−−−−−−−+
然后在第三个之后：
+−−−−−−−−−−−−−−+
k−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+−>| Object@REF#6 |
| +−−−−−−−−−−−−−−+
| | val: 2 |
+−−−−−−−−−−−−−−+ | +−−−−−−−−−−−−−−+
+−>| Object@REF#4 | |
| +−−−−−−−−−−−−−−+ |
| | val: 1 | |
+−−−−−−−−−−−−−−+ | +−−−−−−−−−−−−−−+ |
+−>| Object@REF#2 | | |
| +−−−−−−−−−−−−−−+ | |
| | val: 0 | | |
| +−−−−−−−−−−−−−−+ | |
| | |
| | |
+−−−−−−−−−−+ | | |
arr−−−>| Array | | | |
+−−−−−−−−−−+ +−−−−−−−−−−−−−−−−−+ | | |
| 0: REF#1 |−−−−−−>| Function@REF#1 | | | |
| 1: REF#3 |−−−−+ +−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ | | |
| 2: REF#5 |−−+ | | [[Environment]] |−−>| Environment | | | |
+−−−−−−−−−−+ | | +−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ | | |
| | | j: REF#2 |−+ | |
| | +−−−−−−−−−−−−−+ | |
| | +−−−−−−−−−−−−−−−−−+ | |
| +−>| Function@REF#3 | | |
| +−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ | |
| | [[Environment]] |−−>| Environment | | |
| +−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ | |
| | j: REF#4 |−−−−−−−−−−−−−−−−−−−−−+ |
| +−−−−−−−−−−−−−+ |
| +−−−−−−−−−−−−−−−−−+ |
+−−−>| Function@REF#5 | |
+−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ |
| [[Environment]] |−−>| Environment | |
+−−−−−−−−−−−−−−−−−+ +−−−−−−−−−−−−−+ |
| j: REF#6 |−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
+−−−−−−−−−−−−−+
答案 1 :(得分：1)
使用k = {"val" : i};您正在创建一个新对象并将其分配给k。请改为var k = {}和k.val = i。
答案 2 :(得分：-2)
你找到了一种使用闭包的好方法。使用诸如数字之类的原语，javascript将值创建/复制到新变量中，这就是为什么你看到0,1,2。
选中此示例：https://jsfiddle.net/hrjLvgr9/
请注意arr[0]，arr[1]和arr[2]如何按预期返回3。
var arr = [];
var k;
for(var i = 0; i < 3; i++) {
arr.push(function() {
console.log(i)
})
}
for(var i = 0; i < 3; i++) {
(function(j) {
arr.push(function() {
console.log(j)
})
})(i)
}
arr[0]()
arr[1]()
arr[2]()
arr[3]()
arr[4]()
arr[5]()