從零開始的全棧工程師——js篇（作用域 this 原型筆試題練習）
阿新 • • 發佈：2018-12-02
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.
//5.
function fn () { console.log(5) fn() } fn()//6.
function fn () { console.log(12) } var as = fn() console.log(as)//7.
//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.
// 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); //指向誰？
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); // 指向誰
this.val *= 2;
console.log(this.val); // ???
console.log(val); // ???
}
}
var ff = obj.dbl()
原型
待定