javascript hoisting for global variable

问题

I was wondering how javascript hoisting works for global variable.

Let's say I have following code snippet:

var a = 5;
function print(){
    console.warn("a",a,b);
    var a = 10;
    b=5;
    console.warn("a",a);
}
print();

In this case I am getting error "b is not defined". I wonder why Javascript hoisting is not working for global variable. I tried to look for this but getting results only for variable hoisting. Any thoughts??

回答1:

var statements are hoisted. function declarations are hoisted. Assignments are not hoisted (to the extent that if you combine a var statement with an assignment (var foo = 1) then the declaration part is hoisted but the assignment is not).

来源：https://stackoverflow.com/questions/26753166/javascript-hoisting-for-global-variable