<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>声明提升</title>
</head>
<body>
<script>
//题目1
/*var str1 = "hello";
console.log(str1); */
//题目2
/*console.log(str2); //报错
age = 21;*/
//题目3
/* console.log(str3);// 报错 没有var 不提升
str3 = 'hello'; */
//题目4
// console.log(str4); // underfinde
// var str4 = 'hello';
//题目5
// var str5 = "hello";
// function fn(){
// console.log(str5);//hello
// }
// fn();
//题目6
/*var str6 = "hello";
function fn(){
console.log(str6);//hello
str6 = "world"; // 没有var 不提升
}
fn();*/
//题目7
/*var str7 = "hello";
function fn(){
console.log(str7);//underfind
var str7 = "world";
}
fn();*/
//题目8
/*var arr1 = [1,2,3];
function fn(){
if(typeof arr1 == "undefined"){//type 返回array
arr1 = [];
}
console.log(arr1.length); //3
}
fn();*/
//题目9
// var arr2 = [1,2,3];
// function fn(){
// if(typeof arr2 == "undefined"){
// var arr2 = []; //var 隔着if 提升
// }
// console.log(arr2.length); //0
// }
// fn();
//题目10
// console.log(typeof fn1);//function
// function fn1(){}
//题目11
/*console.log(typeof fn2);//underfind
var fn2 = function(){}*/
//题目12
/*var str = "hello";
function fn(){
console.log(str);//hello
function fn1(){
console.log(str);//underfind
var str = "world";
console.log(str);//world
console.log(this.str);//hello
function fn2(){
console.log(str);//world
str = "world2";
console.log(str);//world2
console.log(this.str);//hello
}
fn2();
console.log(str);
str = "world3";
}
fn1();
console.log(str);
}
fn();
console.log(str);*/
// var str = 4;
// function fn(str){
// console.log(str);
// str = 2;
// console.log(str);
// console.log(this.str);
// console.log(str == this.str);
// }
// fn(str);
// console.log(str);
// function fn(obj){
// obj.name = "hello";
// obj = new Object();
// obj.name = "world";
// console.log(obj.name);
// }
// var person = new Object();
// fn(person);
// console.log(person.name);
// console.log(person instanceof Object);
</script>
</body>
</html>
