定义变量的逗号运算符

Question

我对用于将字符串拆分为表达式的逻辑很感兴趣。

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comma_Operator 说

The comma operator evaluates each of its operands (from left to right) and returns the value of the last operand.

问题是：

如果我有一串代码

 var x = 1, y = 2, z = 3;

我在哪里可以读到为什么 js 将其识别为

var (x = 1), (y = 2), (z = 3);

而不是

var x = (1, y = 2, z = 3); // => x should be 3

Answer 1

您看错了地方 - 您应该查看 var 定义： https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Statements/var

基本上，var 的语法如下：
var varname1 [= value1] [, varname2 [= value2] ... [, varnameN [= valueN]]]];