在这段代码片段中递归是如何发生的? [英] How recursion takes place in this code snippet?

问题描述

查看调用堆栈和监视，现在当我按 F10 时，监视"中的行的值更改为对象对象"，因此一切都发生了，我了解直到此时和之后发生的流程不清楚.现在在病房里，为什么即使我在第 8 行提供断点代码也不会停在第 8 行

Look at the call Stack and Watch, Now when i press F10, the line's value in "Watch" changes to be "object Object" and because of that everything happens, i understand the flow till this time and afterwards what happen is not clear. Now on wards, why does the code doesn't stop at line 8 even if I Provide a break point at line 8

这是关于stackoverflow

我正在尝试理解这段代码

I am trying to understand this code snippet

function assign(obj, prop, value) {
    if (typeof prop === "string")
        prop = prop.split(".");

    if (prop.length > 1) {
        var e = prop.shift();
        assign(obj[e] =
                 Object.prototype.toString.call(obj[e]) === "[object Object]"
                 ? obj[e]
                 : {},
               prop,
               value);
    } else
        obj[prop[0]] = value;
}

var obj = {},
    propName = "foo.bar.foobar";

assign(obj, propName, "Value");

递归是如何发生的，因为函数没有返回任何东西?内部调用中的参数值如何随着最顶层调用堆栈(分配函数)中的函数而改变?

How recursion is happening, as the function is not returning anything ? How the value of the arguments in the inner call being changed as the function in the top most call stack(of assign function) is completed ?

感谢大家的回答，但我的确切问题是它在这一行(第 8 行)中是如何发生的.

Thanks all for answers but my exact question i how its happening in this particular line (line 8).

推荐答案

Object.prototype.toString.call(obj[e]) === "[object Object]" 永远不会为真.它总是 "[object Undefined]"

Object.prototype.toString.call(obj[e]) === "[object Object]" is never true. It is always "[object Undefined]"

1. 开头:

obj:: {}
prop:: 'foo.bar.foobar'

从内部函数(if)第一次调用之前:

obj:: {foo: {}}
prop:: ['bar', 'foobar']

在第二次调用内部函数之前(if):

obj:: {foo: {bar: {}}}
prop:: ['foobar']

最后执行时，因为 prop.length 为 1(else - 不再递归):

At last execution, as prop.length is 1 (else - no more recursion):

obj:: {foo: {bar: {foobar: 'Value'}}}
prop:: []

Javascript 中的对象总是作为引用传递，参考@Tiny Giant 的评论.

Objects in Javascript are always passed as Reference, refer to @Tiny Giant's comment.

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