javascript - 数组不同时如何更改类别？

Question

我知道标题很奇怪，但我不知道如何用一句话表达我的问题。

所以我需要数组和一个文件。我合并了两个数组，所以我可以使用 Math.floor(Math.random() * number)

但是当我的文件的值来自第一个或第二个数组时，我想更改 category.innerHTML。

我尝试了 if 语句，但我猜我错了。

let fruit = ["apple", "mango", "watermelon", "peach", "banana"];

let vegetable = ["cucumber", "carrot", "potato", "celery", "radish"];

let categories = fruit.concat(vegetable);

let categoriesLength = categories.length;

let password = categories[Math.floor(Math.random() * categoriesLength)];

let category = document.querySelector(".category");

if (password <= categories[4]) {
  category.innerHTML = "<p>category: fruit</p>";
} else if (password <= categories[9] && password >= categories[5]) {
  category.innerHTML = "<p>category: vegetable</p>";
}

Answer 1

password <= categories[4]只是按字典顺序比较password使用字符串 banana .

相反，您可以使用 indexOf 或 includes 像这样:

let fruit = ["apple", "mango", "watermelon", "peach", "banana"],
    vegetable = ["cucumber", "carrot", "potato", "celery", "radish"],
    categories = fruit.concat(vegetable),
    categoriesLength = categories.length,
    password = categories[Math.floor(Math.random() * categoriesLength)],
    category = document.querySelector(".category");

if (categories.indexOf(password) <= 4)
  category.innerHTML = "<p>category: fruit</p>";
else
  category.innerHTML = "<p>category: vegetable</p>";

// Supported only in ES2016+
if (fruit.includes(password))
  console.log("category: fruit")
else
  console.log("category: vegetable")

<span class="category" />