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JAVAweb-JS基本数据类型,变量,DOM,pop,push函数,事件

article 2025/2/25 2:45:58

JavaScript,可以嵌套在静态页面中添加一些动态语言.

JavaScript是开发web脚本语言,但也被用到了很多非浏览器环境中,比如node平台

JS可以嵌套在静态页面中可以给静态页面添加一些动态效果(脚本语言),不同浏览器厂商(在浏览器中都有内置解析器解析JS语法)

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
</html>
<script>
    //警告框
    alert("hello world");
   //提示框
   prompt("姑娘你的名字");
   prompt("姑娘你的年龄",18);
</script>
<script>
    console.log("hello world");
    console.log(123);
    console.log(undefined);
    console.log(null);
    console.log(typeof 123);
</script>

<script>
    var num;
    num=3;
    console.log(num);
    var a=100;
    var b=200;
    var c=300;
    console.log(a,b,c);
</script>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
</html>
<script>
    function fun(){
        console.log("白毛浮绿水");
        console.log("红掌拨清波");
    }
    fun();
    function sum(a,b){
        console.log(a+b);
    }
    sum(100,200);
    sum("大华","小华");
</script>

JS函数当中没有重载的问题,永远是后者覆盖前者.

return后面的语句不再执行

return可以在函数体汇总将计算完结果返回,在函数体中使用

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
</html>
<script>
    function fun(){
        console.log("白毛浮绿水");
        console.log("红掌拨清波");
    }
    fun();
    function sum(a,b){
        console.log(a+b);
    }
    sum(100,200);
    sum("大华","小华");
    
</script>

pop:是数组的一个方法,主要的作用是可以在数组尾巴处移除一项元素,

pop方法有返回数值,返回的是移除掉的那项元素.

push:是数组方法,主要的作用是可以向数组添加一个或多个元素.

reverse:数组元素进行倒置

indexof

join,concat

slice切割数组

splice

Dom

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
</html>
<script>
    console.log(document);
    console.log(document.documentElement);
    console.log(document.head);
    console.log(document.body);
    console.log(document.title);
</script>

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div>
        我是表单元素:<input type="text" value="我是表单元素" id="cur">
        <a href="http:\\www.baidu.com" id="box">我是超链接</a>
    </div>
</body>
</html>
<script>
    var cur = document.getElementById('cur');
    console.log(cur);
    console.log(cur.value);
    cur.value = '我是修改后的表单元素';
    var box=document.getElementById('box');
    console.log(box.innerHTML);
    box.innerHTML = '我是修改后的超链接';
</script>