js题库全集

https://leetcode-cn.com/problemset/all/

题目一：

function U(data){
console.log(data,1);
var instance = this;
U = function(){
console.log(data,2);
return instance;
}
}
var U = (function(){
function U(data){
console.log(data,1);
var instance = this;
// 下面的代码内部函数根本没有执行 
U = function(){
console.log(123);
console.log(data,2);
return instance;
}
}
return U;
})()


var U1 = new U('u1'); 
console.log(U1); 
var U2 = new U('u2');
console.log(U2);
console.log(U1 === U2);

题目二：

https://segmentfault.com/q/1010000003017312
var c = (function(){
return function a(){
a = 123;
console.log(a);
return a;
}
})()

c();

a在函数中没有被赋值 这种情况下a是不能被赋值的
命名函数表达式的函数名不能重写
var c = function a() {a = 111; console.log(9)}
c()//9
console.log(a);//报错

var n = function(){d = 111;console.log(9);}
n();//9
console.log(d);//111

function a(){a = 111;console.log(a)}
var c = a;
a() //111
c() //111