为数组内的变量赋值

Question

I'm pretty new to coding and can't find out why this is outputting undefined:

var var0, list = [var0];
list[0] = true;
console.log(var0)

Answer 1

On line 1 you copy the value of var0 into the array.

On line 2 you replace the value in the array.

This doesn't have any effect on var0 . That is just a variable that used to have a copy of the same value . It is not a reference.

Answer 2

You never use or define the value of var0.

list[0] = true;

This line replaces the value of the object in the 0 position (which is var0 because of the first line) to a boolean variable with the value "true".

What you mean to do is

var var0 = true, list = [var0];
console.log(list[0])