<!DOCTYPE html>
<html>
<body>
<h1>JavaScript 运算符</h1>
<p>赋值运算符 += 串联字符串。</p>
<p id="demo"></p>
<script>
txt1 = "Hello ";
txt1 += "Kitty！";
document.getElementById("demo").innerHTML = txt1;
</script>
</body>
</html>