分配关联性[重复](Assignment associativity [duplicate])

 
 
 这个问题在这里已有答案： 
 
 
 
  
 Javascript代码技巧：foo.x 4答案 的价值是什么 
 
 
 
 
 赋值运算符具有从右到左的关联性。 所以 
 
var x,y;
x=y=1;
 
 按预期工作，x等于1.现在考虑代码： 
 
var foo={};
foo.x = foo = {n: 2};
 
 我希望以上工作方式如下： 
 
var foo = {n: 2}; 
foo.x=foo;
 
 但是，在第一种情况下，foo.x undefined而在第二种情况下， foo.x points to foo （循环引用）。 任何解释？ 

 
 
This question already has an answer here:
 
 
 
  
 JavaScript code trick: What's the value of foo.x  6 answers  
 
 
 
 
The assignment operator has right-to-left associativity. So 
 
var x,y;
x=y=1;
 
works as expected and x equals 1. Consider now the code:
 
var foo={};
foo.x = foo = {n: 2};
 
I would expect the above to work like the following:
 
var foo = {n: 2}; 
foo.x=foo;
 
However, in the first case foo.x is undefined while in the second case foo.x points to foo (circular reference). Any explanation?

原文：https://stackoverflow.com/questions/37763113