javascript - javascript 中的 if 语句和作用域

Question

编辑:添加对象

我遇到了一个问题，在函数体内声明的变量在从函数返回变量之前似乎就消失了:

var customerData = {
  'Joe': {
    visits: 1
  },
  'Carol': {
    visits: 2
  },
  'Howard': {
    visits: 3,
  },
  'Carrie': {
    visits: 4
  }
};

function greetCustomer(firstName) {
  var greeting = '';

  for(var key in customerData){
    if(key === firstName){
      if(customerData[key]['visits'] === 1){
         greeting = "Welcome back, " + firstName + "! We're glad you liked us the first time!";
        console.log(greeting); // here to illustrate issue
      }
      else if(customerData[key]['visits'] > 1){
        greeting = "Welcome back, " + firstName + "! So glad to see you again!";
        console.log(greeting);
      }
    }
    else{
      greeting = "Welcome! Is this your first time?"
    }
  }

  return greeting;
}
greetCustomer("Joe");

输出:

Welcome back, Joe! We're glad you liked us the first time! // here is the correct greeting from the console output
=> 'Welcome! Is this your first time?' // this is what I got
Welcome back, Carol! So glad to see you again! // correct output again
=> 'Welcome! Is this your first time? // base case again.

greeting 不应该在整个函数中可见，以便访问其值和进行赋值吗？我知道我可以从分支返回问候语，但我不确定我在这里看到的是什么，但我希望有人能解释一下。谢谢。

Answer 1

对于成功条件，立即返回问候语，而不是将其分配给greeting变量。但对于 firstname 不是 customerData 中的键之一的情况，只需将 greeting 设置为 “欢迎!这是您第一次吗？” ?" & 让迭代继续寻找 `firstname.

将您的代码更改为此[已测试]:

function greetCustomer(firstName) {
var greeting = '';

for(var key in customerData){
  if(key === firstName){
    if(customerData[key]['visits'] === 1){
      return("Welcome back, " + firstName + "! We're glad you liked us the first time!");
      console.log(greeting); // here to illustrate issue
    }
    else if(customerData[key]['visits'] > 1){
      return("Welcome back, " + firstName + "! So glad to see you again!");
     }
   }
   else{
    greeting = "Welcome! Is this your first time?";
  }
}
return greeting;
}
console.log(greetCustomer("Joe"));