How to understand var = a = b = C = 9? How to pre parse?

 

JavaScript The code is pre parsed in such a process ：

ａ Private quantity .

ｂ,ｃ Is a global variable .

　　　　　var a = b = c = 9;// This is not a collective statement ( Collective declarations shall be separated by commas )
        // It's equivalent to ：
        var a = 9; b = 9; c = 9;


        // The right way to make a collective statement ：
        var a = 9, b = 9, c = 9;