js参数默认值对函数length 和arguments影响

function Foo(a,b){  
    console.log(a==arguments[0],b==arguments[1]);
    console.log(a,b);
    a='44';
    b='555';
    console.log(a==arguments[0],b==arguments[1]); //若Foo(a,b=3)设置默认值（相当于'use strice' 此时不相等 Foo.length:1 
}
Foo(10,1)
console.log(Foo.length) //1