javascript - 使用JavaScript进行多次左手分配(Multiple left-hand assignment with JavaScript)

Question

var var1 = 1,
    var2 = 1,
    var3 = 1;

This is equivalent to this:

(这相当于：)

var var1 = var2 = var3 = 1;

I'm fairly certain this is the order the variables are defined: var3, var2, var1, which would be equivalent to this:

(我很确定这是变量定义的顺序：var3，var2，var1，它等价于：)

var var3 = 1, var2 = var3, var1 = var2;

Is there any way to confirm this in JavaScript?

(有没有办法在JavaScript中确认这一点？)

Using some profiler possibly?

(可能使用一些分析器？)

  ask by David Calhoun translate from so

Answer 1

Actually,

(其实，)

var var1 = 1, var2 = 1, var3 = 1;

is not equivalent to:

(不等于：)

var var1 = var2 = var3 = 1;

The difference is in scoping:

(区别在于范围界定：)

 function good() { var var1 = 1, var2 = 1, var3 = 1; } function bad() { var var1 = var2 = var3 = 1; } good(); console.log(window.var2); // undefined bad(); console.log(window.var2); // 1. Aggh! 

Actually this shows that assignment are right associative.

(实际上这表明赋值是正确的关联。)

The bad example is equivalent to:

(bad例子相当于：)

var var1 = (window.var2 = (window.var3 = 1));