如何阻止我的程序连续两次输出相同的内容？

Question

因此，我创建了这个包含一些 JavaScript 的 HTML 页面。我有这个按钮可以输出六分之一的表情符号。它工作正常，然后我添加了一些代码来阻止程序连续两次输出相同的表情符号，但它没有任何区别，我不知道为什么。

这是我的代码：

function randEmoji()

        {

            var oldEmoji = emoji;

            var emojiList = [";)", ":D", "xD", ":O", ":X", ":P"];

            var emoji = emojiList[Math.floor(Math.random() * emojiList.length)];

            if (oldEmoji == emoji)

            {

                randEmoji();

            }

            else

            {

                document.getElementById("emojiText").innerHTML = "Look how fun! ---> " + emoji + " <--- An emoji!";

                console.log(emoji);

            }

        }

我不太擅长编程，也不知道是什么导致了这个问题。

Answer 1

您必须在函数外部声明变量并将它们设置在函数内部。否则它们的值在每次函数调用中都会被重置。尝试这个：var oldEmoji = '';var emoji = '';var emojiList = [";)", ":D", "xD", ":O", ":X", ":P"];function randEmoji() {&nbsp; &nbsp; oldEmoji = emoji;&nbsp; &nbsp; emoji = emojiList[Math.floor(Math.random() * emojiList.length)];&nbsp; &nbsp; if (oldEmoji == emoji) {&nbsp; &nbsp; &nbsp; &nbsp; randEmoji();&nbsp; &nbsp; } else {&nbsp; &nbsp; &nbsp; &nbsp; console.log(emoji);&nbsp; &nbsp; }}var i = 0;while (i < 20) {&nbsp; &nbsp; randEmoji();&nbsp; &nbsp; i += 1;}

Answer 2

问题在于函数作用域的任何局部变量（意味着在函数内部声明）在函数完成执行后都会被丢弃。因此，每次运行该函数emoji并oldEmoji从undefined一种解决方案是将其中一个声明移动到父范围，如下所示：var oldEmoji;function randEmoji() {&nbsp; &nbsp; var emojiList = [";)", ":D"];&nbsp; &nbsp; var emoji = emojiList[Math.floor(Math.random() * emojiList.length)];&nbsp; &nbsp;&nbsp;&nbsp; &nbsp; if (oldEmoji == emoji) {&nbsp; &nbsp; &nbsp; &nbsp; randEmoji();&nbsp; &nbsp; } else {&nbsp; &nbsp; &nbsp; &nbsp; console.log(emoji);&nbsp; &nbsp; &nbsp; &nbsp; oldEmoji = emoji;&nbsp; &nbsp; }}randEmoji();randEmoji();randEmoji();randEmoji();randEmoji();randEmoji();randEmoji();看这里，我们实际上从来没有重复过。

Answer 3

var oldEmoji = '';&nbsp; &nbsp; &nbsp; var emoji = '';&nbsp; &nbsp; &nbsp; var emojiList = [";)", ":D", "xD", ":O", ":X", ":P"];&nbsp; &nbsp; &nbsp;&nbsp;&nbsp; &nbsp; function randEmoji(){&nbsp; &nbsp; &nbsp; &nbsp;// remove old emoji first to avoid doing a recursive call&nbsp; &nbsp; &nbsp; &nbsp;var check = oldEmoji? emojiList.filter(e => e !== oldEmoji ) :&nbsp; emojiList;&nbsp; &nbsp; &nbsp; &nbsp;var emoji = check[Math.floor(Math.random() * check.length)];&nbsp; &nbsp; &nbsp; &nbsp;oldEmoji = emoji&nbsp; &nbsp; &nbsp; &nbsp;document.getElementById("emojiText").innerHTML = "Look how fun! ---> " + emoji + " <--- An emoji!";&nbsp; &nbsp; &nbsp; &nbsp;console.log(emoji);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp; }