js面试题

Posted 2022-09-01 wenghao

var v = 123;
function foo()
    var v = 456;
    function inner()
        console.log(v)
    
    return inner


result = foo()
console.log(result())

# 问输出结果：NULL

Name=‘root‘;
Age = 18;
function Foo(name,age)
    this.Name = name;
    this.Age = age;
    this.Func = function()
        // this=obj
        console.log(this.Name,this.Age);
        (function()
             console.log(this.Name,this.Age);
        )();
    

obj = new Foo(‘alex‘,666);
obj.Func()
# 问输出结果：
alex 666
root 18






1. js面向对象

function Func(name,age)
    this.Name = name;
    this.Age = age;  

obj = new Func(‘root‘,18)

2. this关键字
# 每个函数中都有this
# 函数调用时，this=window
# 类new时，   this=obj

function func()
    # 当做函数执行函数时，this=window
    console.log(this);

func()


function Func()
    # his=obj
    console.log(this);

obj = new Func()


3. js中无字典，只有对象

Name = ‘alex‘
obj = 
    Name: ‘root‘,
    Age: 18,
    Func: function()
        # this=obj
        console.log(this.Name) # root 
        
        function inner()
            # this=window
            console.log(this.Name)#alex
        
        inner()#函数的调用方式window
    

相当于new了对象 obj

obj.Func()就等于obj



Name = ‘alex‘
obj = 
    Name: ‘root‘,
    Age: 18,
    Func: function()
        # this=obj
        console.log(this.Name) # root 
        var that =this;#修改的地方，那么that这时也是obj
        function inner()
            # 这里面this=window
            console.log(that.Name)这里的that等于obj
        
        inner()
        // 子执行函数
        (function()
            console.log(that.Name)
        )()
    

相当于new了对象 obj

obj.Func()