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JavaScript基础(十二)——BOM

左小米z 2022-04-16 阅读 83
javascript

一、简介

二、window对象(全局对象)

(1)window.setTimeout()等

我们之前学过的,如setTimeout()方法,其实完整的写法是window.setTimeout()。

    <script>
        window.setTimeout(() => {
            console.log("hello world!")
        }, 1000)
    </script>

(2)自定义的全局函数(window.fun())

    <script>
        function fun() {
            console.log("hello world");
        }

        window.fun();
    </script>

控制台输出:

(3)window.alert()

    <script>
        window.alert("hello world");
    </script>

(4)window.prompt()

    <script>
        let str = window.prompt("请输入内容:", "你好!");
        console.log(str);
    </script>

 效果如下:

分析:

(5)window.confirm()

    <script>
        let result = window.confirm("是否删除该条数据?");
        console.log(result);
    </script>

效果如下:

分析:

(6)案例一——猜数字

    <script>
        // 生成【1,100】的随机数
        let targetNumber = Math.floor(Math.random() * 100 + 1);

        // 递归函数:在函数内部,多次调用该函数
        function guessNumber() {
            let number = prompt("请输入数字:");
            if (number == targetNumber) {
                alert("恭喜你回答正确!");
            } else if (number > targetNumber) {
                alert("大于目标数字,请再猜一次");
                guessNumber();
            } else if (number < targetNumber) {
                alert("小于目标数字,请再猜一次")
                guessNumber();
            } else {
                alert("格式错误,请重新输入!")
                guessNumber();
            }
        }
        
        guessNumber();
    </script>

效果如下:

(7)案例二——删除水果的提示框 

<body>
    <ul>
        <li>苹果</li>
        <li>鸭梨</li>
        <li>香蕉</li>
    </ul>
    <script>
        let ul = document.querySelector("ul");
        ul.onclick = function (e) {
            let result = confirm("是否删除该水果?")
            if (result) {
                ul.removeChild(e.target);
            }
        }
    </script>
</body>

效果如下:

分析:

 三、location对象

(1)随便打开一个网址,输入各种属性,查看结果。

如:

反ins社交App真的开始默默生长了?https://m.thepaper.cn/baijiahao_17638219并打开控制台,分别输入:

输出如下: 

 (2)跳转网页(location.href())

<body>
    <button>百度</button>
    <script>
        let btn = document.querySelector("button");
        btn.onclick = function () {
            location.href = "https://www.baidu.com";
        }
    </script>
</body>

效果如下:

分析:

四、Navigator(获取访问者的浏览器信息)

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Demo35</title>
</head>

<body>
    <script>
        let equipment = checkagent(navigator.userAgent);
        console.log(equipment);

        function checkagent(ua) {
            let isWindowsPhone = /(?:Windows Phone)/.test(ua),
                isSymbian = /(?:SymbianOS)/.test(ua) || isWindowsPhone,
                isAndroid = /(?:Android)/.test(ua),
                isFireFox = /(?:Firefox)/.test(ua),
                isChrome = /(?:Chrome|CriOS)/.test(ua),
                isTablet = /(?:iPad|PlayBook)/.test(ua) || (isAndroid && !/(?:Mobile)/.test(ua)) || (isFireFox && /(?:Tablet)/.test(ua)),
                isPhone = /(?:iPhone)/.test(ua) && !isTablet,
                isPc = !isPhone && !isAndroid && isSymbian,
                isWechat = /(?:MicroMessenger)/.test(ua);
            let equipment = {
                isTablet: isTablet,
                isPhone: isPhone,
                isAndroid: isAndroid,
                isChrome: isChrome,
                isPc: isPc,
                isWechat: isWechat
            };
            if (equipment.isAndroid) {
                return "安卓手机";
            } else if (equipment.isPhone) {
                return "苹果手机";
            } else if (equipment.isTablet) {
                return "平板";
            } else if (equipment.isPc) {
                return "电脑";
            }else if(equipment.isChrome){
                return "谷歌浏览器";
            }
        }
    </script>
</body>

</html>

效果如下:

分析:

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