如何将提示响应与我的变量进行比较？

Question

用户应该在提示框中输入几个名字之一。如果他们的回答不是给定的名字之一，他们会被告知这不是有效的回答。然而，如果他们这样做了，他们就会被告知他们选择了谁。问题是，无论我输入什么，它总是说这是一个无效的名称。任何建议如何解决这个问题？

 <html>
<body bgcolor = "firebrick">
    <title>Dinner Plans</title>
    <center><h1><b> Dinner Plans</h1>
        <p> Guests to Pick From:</p></b>
        <p> Jane, Lisa, Taylor, Chris, Alyssa, Will and Jessica </p>
       <button onclick="Invites()">Click To Invite</button>
  <div id = "Coming"></div>
<script>
function Invites() {
var txt;
var person = prompt("Who is Coming For Dinner?", "Enter Names Here");
if (person == null || person != guest) {
    txt = "Not A Valid Guest.";
} 
else {
    txt = "Your Invited Guests Are:" + person;
}
document.getElementById("Coming").innerHTML = txt;
}

function guest ( slices , toppings ) {
  this.numSlices = slices;
  this.numToppings = toppings; 
}
var Jane = new guest( 2, "Mushroom", "Onions", "Peppers", "Olives");
var Lisa = new guest(3, "Pepperoni", "Ham", "Pineapple");
var Taylor = new guest(3, "Extra Cheese", "Pepperoni", "Sausage", "Bacon");
var Chris = new guest(2, "Mushroom", "Sausage", "Bacon", "Ham", "Onion", "Peppers");
var Alyssa = new guest(1, " Pepperoni", "Bacon");
var Will = new guest(2, "Extra Cheese", "Sausage", "Bacon", "Onion", "Peppers", "Olives");
var Jessica = new guest(2, "Pepperoni", "Bacon", "Ham", "Pineapple", "Onion", "Peppers");

if (Invites == null || Invites == "") {
    txt = " You invited zero guests, you have a pizza all to yourself!";
} else { 
    txt = " You Invited:" + Invites; 
}

        </script>

Answer 1

<script>
function Invites() {
    var txt;
    var guestArray = [
        "Jane",
        "Lisa",
        "Taylor",
        "Chris",
        "Alyssa",
        "Will",
        "Jessica"
    ];

    var person = prompt("Who is Coming For Dinner?", "Enter Names Here");
    if (person == null || guestArray.indexOf(person) === -1) {
        txt = "Not A Valid Guest.";
    } 
    else {
        txt = "Your Invited Guests Are:" + person;
    }

    document.getElementById("Coming").innerHTML = txt;
}

function guest ( slices , toppings ) {
    this.numSlices = slices;
    this.numToppings = toppings; 
}

var Jane = new guest( 2, "Mushroom", "Onions", "Peppers", "Olives");
var Lisa = new guest(3, "Pepperoni", "Ham", "Pineapple");
var Taylor = new guest(3, "Extra Cheese", "Pepperoni", "Sausage", "Bacon");
var Chris = new guest(2, "Mushroom", "Sausage", "Bacon", "Ham", "Onion", "Peppers");
var Alyssa = new guest(1, " Pepperoni", "Bacon");
var Will = new guest(2, "Extra Cheese", "Sausage", "Bacon", "Onion", "Peppers", "Olives");
var Jessica = new guest(2, "Pepperoni", "Bacon", "Ham", "Pineapple", "Onion", "Peppers");

if (Invites == null || Invites == "") {
    txt = " You invited zero guests, you have a pizza all to yourself!";
} else { 
    txt = " You Invited:" + Invites; 
}

</script>


<title>Dinner Plans</title>
<center><h1><b> Dinner Plans</h1>
<p> Guests to Pick From:</p></b>
<p> Jane, Lisa, Taylor, Chris, Alyssa, Will and Jessica </p>
<button onclick="Invites()">Click To Invite</button>
<div id = "Coming"></div>

所以你的代码存在以下问题：

guest 是构造函数。不是一个值（客人的名字）你是期待。
比对提示填写的名称，需要有效列表名字.
为此，您可以使用名称数组（此处为 guestArray）。
我使用了 indexOf 函数，它在 Array 实例上可用 javascript。它 returns -1 当没有找到匹配时元素的数组或索引（如果存在匹配项）。

如何将提示响应与我的变量进行比较？

How do I compare the prompt response to my variable?

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function