Firefox: 71.0 (64)
When you click the button, observe the console, the value printed twice is different。
Why is this so?
The source code is below
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
textarea {
letter-spacing: normal;
line-height: 1;
padding-top: 10px;
padding-bottom: 10px;
font-family: "Monospaced Number", "Chinese Quote", -apple-system, system-ui, "Segoe UI", Roboto, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
font-weight: 400;
font-size: 13px;
text-rendering: optimizeLegibility;
text-transform: none;
width: 178px;
text-indent: 0px;
padding-left: 10px;
padding-right: 10px;
border-width: 1px;
box-sizing: content-box;
min-height: 0 !important;
max-height: none !important;
height: 13px !important;
visibility: hidden !important;
overflow: hidden !important;
position: absolute !important;
z-index: -1000 !important;
top: 0 !important;
right: 0 !important;
}
</style>
</head>
<body>
<button id="btn">btn</button>
<script>
document.getElementById('btn').addEventListener('click', () => {
hiddenTextarea = document.createElement('textarea');
document.body.appendChild(hiddenTextarea);
console.log(hiddenTextarea.scrollHeight)
hiddenTextarea.value = 'sfdsf'
console.log(hiddenTextarea.scrollHeight)
})
</script>
</body>
</html>