作用域

// 1.

fn() function fn () { console.log(12) } var as = function () { console.log(45) }

// 2.

var a = 12; function fn () { console.log(a) var a = 45; console.log(a) } fn()

//3.

var a = 12; function fn () { console.log(a) a = 45; console.log(a) } fn()

//4.

function fn () { console.log(11) function ff () { console.log(22) } ff() } fn()

//5.

function fn () { console.log(5) fn() } fn()

//6.

function fn () { console.log(12) } var as = fn() console.log(as)

//7.

function fn () { console.log(12); return 45; console.log(456) } var as = fn()

//8.

var a = 12; function fn () { console.log(a); return 4; var a = 45; } fn()

// 9.

var a = 45; function fn () { console.log(a) } fn()

// 10.

var a = 45; function fn (a) { console.log(a) } fn(5)

// 11.

var a = 123; function fun () { alert(a); } fun()

// 12.

var a = 123; function fun () { alert(a); var a = 456; } fun(); alert(a);

// 13.

var a = 123; function fun () { alert(a); a = 456; } fun() alert(a)

// 14.

var a = 123; function fun (a) { alert(a) a = 456; } fun() alert(a)

// 15.

var a = 123; function fun (a) { alert(a) a = 456 } fun() alert(a)  

//16.

function makeNoSense (x) { this.x = x; } makeNoSense(5); console.log(x); function test () { this.x = 1; alert(this.x); } test();    

This

//1.

var name = ‘222‘; var a = { name : ‘111‘, say : function () { console.log(this.name) } }

var fun = a.say; fun() //??? a.say() //???

var b = { name : ‘333‘, say : function (fun) { fun(); } } b.say(a.say); //??? b.say = a.say; b.say() //???  

//2.

var val = 1
var obj = {
val : 2,
dbl : function() {
var val = 45;
console.log(this); //指向谁？
this.val *= 2;
console.log(this.val); //？？
console.log(val); //？？
}
}
var fn = obj.dbl
fn()

//3.

var x = 12;
function test() {
console.log(this.x)
}
test() //??

//4.

var x = 12;
function test() {
console.log(this.x)
}
var obj={
x:45,
ss:test
}
obj.ss() //??

//5.

var x = 12;
function test() {
console.log(this.x)
}
var obj = {
x:45,
ss:function(){
console.log(this)
test()
}
}
obj.ss() //??

//6.

var val = 1
var obj = {
val : 2,
dbl : function() {
// var val = 45;
console.log(this); // 指向谁
this.val *= 2;
console.log(this.val); // ???
console.log(val); // ???
}
}
var ff = obj.dbl()

原型

待定