单元二之第三章函数声明式和函数表达式

问题

const sum10 = (num = 0) => num + 10,
  sum11 = (num = 0) => num + 11,
  sum12 = (num = 0) => num + 12;

console.log("sum10:", sum10());
console.log("sum11:", sum11(11));
console.log("sum12:", sum12(12));

console.log("sum100:", sum100);
// 输出:undefined
console.log("sum100:", sum100());
// 输出:(报错)sum100 is not function
// 原因:执行函数时才会分配给这个变量,它知道的只是它有一个未定义的值,仅此而已

var sum100 = function (num) {
  return num + 100;
};

// 函数声明;
// 函数的作用域:大括号内
//
function sum10(num) {
  return num + 10;
}

var sum100 = function (num) {
  return num + 100;
};

const sum100 = (num) => num + 100;

// 如果只有一个参数
const sum1000 = (num) => num + 1000;

eum API{
  list
}

export const getUserInfo = (data) => {},
  getRegister = (data) => {},
  getUserInfo = (data) => {};

export const setUserInfo =  (data) => {},
setRegister = (data) => {},
setGoodInfo = (data) => {},

总结

1. 箭头函数是一个函数表达式