js面试题

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()