当我有条件 `if (bool = true)` 时，永远不会命中 else 分支。为什么？

Question

挑战如下：

创建一个接受字符串的函数 makePlans。这个字符串应该是一个名字。函数 makePlans 应该调用函数 callFriend 并返回结果。 callFriend 接受一个布尔值和一个字符串。将friendsAvailable变量和名称传递给callFriend。

创建一个接受布尔值和字符串的函数 callFriend。如果布尔值为真，则 callFriend 应返回字符串“本周末使用 NAME 制定的计划”。否则它应该返回“这个周末每个人都很忙”。>

这是我写的：

let friendsAvailable = true;

function makePlans(name) {
  return callFriend(friendsAvailable, name);
}

function callFriend(bool, name) {
  if (bool = true) {
    return 'Plans made with ' + (name) + ' this weekend'
  } else {
    'Everyone is busy this weekend'
  }

}

console.log(makePlans("Mary")) // should return: "Plans made with Mary this weekend'
friendsAvailable = false;
console.log(makePlans("James")) //should return: "Everyone is busy this weekend."

Answer 1

除了大家已经指出的if (bool = true)部分（你可以使用if (bool)），你忘了在else声明中添加return。应该是：

} else {
    return 'Everyone is busy this weekend'
}

Answer 2

完整代码：

let friendsAvailable = true;

function makePlans(name)
  {
  return callFriend(friendsAvailable, name);
  }

function callFriend(bool, name)
  {
  if (bool)  // or  if (bool===true), but testing if true is true is a little bit redundant
    {
    return 'Plans made with ' + (name) + ' this weekend'
    } 
  else 
    {
    return 'Everyone is busy this weekend'
    }
  }

console.log(makePlans("Mary")) // should return: "Plans made with Mary this weekend'
friendsAvailable = false;
console.log(makePlans("James")) //should return: "Everyone is busy this weekend."

但是，如果您想给老师留下深刻印象，请这样做：

const
  callFriend = 
    (bool, name) =>
      bool 
       ? `Plans made with ${name} this weekend` 
       : 'Everyone is busy this weekend' 

const makePlans = name => callFriend(friendsAvailable, name);


let friendsAvailable = true

console.log(makePlans('Mary')) 

friendsAvailable = false

console.log(makePlans('James')) 

一些帮手：
Arrow function expressions
Conditional (ternary) operator