黑色方块出现一秒钟，然后显示带有打字机效果的表情符号

我尝试用表情符号实现JavaScript打字机效果。

问题是：当效果写表情符号时，它会在一秒钟内显示为黑色方形占位符或unicode U+FFFD替换字符，也称为：�,就像在显示表情符号之前需要加载一样。这是代码。

var TxtType = function(el, toRotate, period) {
this.toRotate = toRotate;
this.el = el;
this.loopNum = 0;
this.period = parseInt(period, 10) || 2000;
this.txt = '';
this.tick();
this.isDeleting = false;
};

TxtType.prototype.tick = function() {
var i = this.loopNum % this.toRotate.length;
var fullTxt = this.toRotate[i];

if (this.isDeleting) {
this.txt = fullTxt.substring(0, this.txt.length - 1);
} else {
this.txt = fullTxt.substring(0, this.txt.length + 1);
}

this.el.innerHTML = '<span class="wrap">'+this.txt+'</span>';

var that = this;
var delta = 150 - Math.random() * 100;

if (this.isDeleting) { delta /= 2; }

if (!this.isDeleting && this.txt === fullTxt) {
delta = this.period;
this.isDeleting = true;
} else if (this.isDeleting && this.txt === '') {
this.isDeleting = false;
this.loopNum++;
delta = 500;
}

setTimeout(function() {
that.tick();
}, delta);
};

window.onload = function() {
var elements = document.getElementsByClassName('typewrite');
for (var i=0; i<elements.length; i++) {
var toRotate = elements[i].getAttribute('data-type');
var period = elements[i].getAttribute('data-period');
if (toRotate) {
new TxtType(elements[i], JSON.parse(toRotate), period);
}
}
// INJECT CSS
var css = document.createElement("style");
css.type = "text/css";
css.innerHTML = ".typewrite > .wrap { border-right: 0.08em solid #fff}";
document.body.appendChild(css);
};

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="stylesheet" href="style.css">
<title>Title</title>
</head>
<body>
<div class="emoji">Emoji: <a class="typewrite" data-period="1000" data-type='[ "🍥", "⌚️", "🌊", "📇", "🔆" ]'></a></div>
<script src="index.js" type="text/javascript"></script>
</body>
</html>

如果从字符中分割一个索引，并不是所有字符都能准确表示。表情符号是一个常见的例外-它们通常需要代理对，其中需要两个标记才能正确显示字符。例如：

const str = "🍥";
console.log(str[0]);
console.log(str[1]);
console.log(str.slice(0, 2));

所以，不要从字符串中分割单个标记。而不是做

if (this.isDeleting) {
this.txt = fullTxt.substring(0, this.txt.length - 1);
} else {
this.txt = fullTxt.substring(0, this.txt.length + 1);
}

进行

var fullTxt = [...this.toRotate[i]];
if (this.isDeleting) {
this.txt = fullTxt.slice(0, [...this.txt].length - 1).join('');
} else {
this.txt = fullTxt.slice(0, [...this.txt].length + 1).join('');
}

因为将字符串扩展到数组中会保留代理项对。

var TxtType = function(el, toRotate, period) {
this.toRotate = toRotate;
this.el = el;
this.loopNum = 0;
this.period = parseInt(period, 10) || 2000;
this.txt = '';
this.tick();
this.isDeleting = false;
};
TxtType.prototype.tick = function() {
var i = this.loopNum % this.toRotate.length;
var fullTxt = [...this.toRotate[i]];
if (this.isDeleting) {
this.txt = fullTxt.slice(0, [...this.txt].length - 1).join('');
} else {
this.txt = fullTxt.slice(0, [...this.txt].length + 1).join('');
}
this.el.innerHTML = '<span class="wrap">' + this.txt + '</span>';
var that = this;
var delta = 150 - Math.random() * 100;
if (this.isDeleting) {
delta /= 2;
}
if (!this.isDeleting && this.txt === fullTxt.join('')) {
delta = this.period;
this.isDeleting = true;
} else if (this.isDeleting && this.txt === '') {
this.isDeleting = false;
this.loopNum++;
delta = 500;
}
setTimeout(function() {
that.tick();
}, delta);
};
window.onload = function() {
var elements = document.getElementsByClassName('typewrite');
for (var i = 0; i < elements.length; i++) {
var toRotate = elements[i].getAttribute('data-type');
var period = elements[i].getAttribute('data-period');
if (toRotate) {
new TxtType(elements[i], JSON.parse(toRotate), period);
}
}
// INJECT CSS
var css = document.createElement("style");
css.type = "text/css";
css.innerHTML = ".typewrite > .wrap { border-right: 0.08em solid #fff}";
document.body.appendChild(css);
};

<div class="emoji">Emoji:
<a class="typewrite" data-period="1000" data-type='[ "🍥", "⌚️", "🌊", "📇", "🔆" ]'></a>
</div>

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