JS的变量提升

console.log(v1);
var v1 = 100;
function foo() {
    console.log(v1);
    var v1 = 200;
    console.log(v1);
}
foo();
console.log(v1);

//undefined
//undefined
//200
//100

function bar () {}    //函数声明式
var foo = function () {}     //函数字面量式，这个和变量提升的结果是一样的，函数只是一个具体的值

console.log(bar);
function bar () {
  console.log(1);
}

function bar () {
  console.log(1);
}
console.log(bar);

console.log(a);    // f a() {console.log(10)}
console.log(a());    //  10
var a = 3;

function a() {
    console.log(10) 
}
console.log(a)   // 3
a = 6;
console.log(a());  // 报错：a is not a function;

    var a = funtion () {
        console.log(10)
    }
    var a;
    console.log(a);    //  f a() {console.log(10)}
    console.log(a());  //  10

    a = 3;
    console.log(a)   // 3
    a = 6;
    console.log(a());   // 报错：a() is not a function;