变量提升面试题

1题

console.log(a, b, c);
var a = 12,
    b = 13,
    c = 14;
function fn(a) {
    console.log(a, b, c);
    a = 100;
    c = 200;
    console.log(a, b, c);
}
b = fn(10);
console.log(a, b, c);

2题

var a=1;
var obj ={
   name:"tom"
}
function fn(){
   var a2 = a;
   obj2 = obj;
   a2 =a;
   obj2.name ="jack";
}
fn();
console.log(a);
console.log(obj);

3题

var a = 1;
function fn(a){
    console.log(a)
    var a = 2;
    function a(){}
}
fn(a);

4题

console.log(a); 
var a=12; 
function fn(){
    console.log(a); 
    var a=13;   
}
fn();   
console.log(a);

5题

console.log(a); 
var a=12;
function fn(){
    console.log(a);
    a=13;
}
fn();
console.log(a);

6题

console.log(a);
a=12;
function fn(){
    console.log(a);
    a=13;   
}
fn();
console.log(a);

7题

var foo='hello'; 
(function(foo){
   console.log(foo);
   var foo=foo||'world';
   console.log(foo);
})(foo);
console.log(foo);