var str = ' hello '
console.log(str.trim()） //hello 去除两端空格
var str1 = ' he l l o '
console.log(str.trim()） //he l l o 去除两端空格
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<input type="text"> <button>点击</button>
<div></div>
<script>
// trim 方法去除字符串两侧空格
var str = ' an dy ';
console.log(str);
var str1 = str.trim();
console.log(str1);
var input = document.querySelector('input');
var btn = document.querySelector('button');
var div = document.querySelector('div');
btn.onclick = function() {
var str = input.value.trim();
if (str === '') {
alert('请输入内容');
} else {
console.log(str);
console.log(str.length);
div.innerHTML = str;
}
}
</script>
</body>
</html>