The use of JS variables [pop-up input box, prompt user name to enter name; pop-up a dialog box, output the name just entered by the user]

1. Code

<script>
    //1.输出用户名 并存储到一个变量中
    var myname = prompt('请输入您的名字');
    //2.输出这个用户名
    alert(myname);
</script>

2. Results display

1. Input name

2. Output name

3. Supplementary variables

1. The variable is only declared but not assigned, and the output result is undefined.
2. If a variable is not declared or assigned a value, an error will be reported if a variable is used directly.
3. It can also be used without declaring direct assignment.
4. Try not to use name as a variable name.