要求，完成一个高度和宽度自动扩展的文本输入组件如图所示
pic01.gif
主要思想是textarea的长度和高度分别用一个隐藏的div和一个隐藏的textarea去获取，然后把获取到的长度和高度放入我们的textarea，就实现了这个要求，下面附上代码(用vue实现，原生同理)。
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="utf-8">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<title>自动扩展的文本输入</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<script src="https://cdn.staticfile.org/jquery/1.10.2/jquery.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/vue"></script>
<style>
textarea {
resize: none;
font-family: Arial, Helvetica, sans-serif;
font-size: 16px;
}
#bk {
width: 500px;
padding: 5px;
border-style: solid;
border-color: red;
border-width: 1px 1px 1px 1px;
}
div {
font-family: Arial, Helvetica, sans-serif;
font-size: 16px;
}
</style>
</head>
<body>
<div id="app">
<div id="bk">
<textarea @focus="textFocus" type="text" v-model="content" ref="input"
:style="{height: teaxtAreaHeight,width: teaxtAreaWidth}" rows="1"
style="overflow-y: hidden;"></textarea>
</div>
<textarea style="position: absolute; visibility:hidden; width: 500px;" ref="heightRuler" v-model="content"
rows="1"></textarea>
<div style="position: absolute;visibility:hidden;" ref="widthRuler">{{content}}</div>
</div>
</body>
<script type="text/javascript">
var app = new Vue({
el: '#app',
data: {
content: '',
teaxtAreaHeight: '',
teaxtAreaWidth: '120px'
},
methods: {
textFocus() {
document.addEventListener('keyup', () => {
this.$nextTick(() => {
const width = (this.$refs.widthRuler).offsetWidth + 10;
console.log(width);
if (width !== this.teaxtAreaWidth && width < 500 && width > 120) {
this.teaxtAreaWidth = width + 'px';
}
const height = `${(this.$refs.heightRuler).scrollHeight}px`;
if (height !== this.teaxtAreaHeight) {
this.teaxtAreaHeight = height;
}
});
});
}
}
})
</script>
</html>
