js的惰性声明, js中声明过的变量(预解释),后在不会重新声明了
fn(); ?// 声明+定义 js中声明过一次的变量,之后在不会重新声明了function fn() { ???console.log("ok")}fn(); //okfn = 22; //赋值是允许的fn(); // Uncaught TypeError: fn is not a functionfunction fn() { console.log("ok !!!");}fn(); //Uncaught TypeError: fn is not a function