JS相关

好玩的~

1、倒计时效果
代码

<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no,viewport-fit=cover">
    <title>Page Title</title>
</head>

<body>
    <div class="wrap">
        <div class="over">本场距离结束还剩</div>
        <div class="time">
            <span class="hour"></span>:
            <span class="minute"></span>:
            <span class="second"></span>
        </div>
    </div>
    <script>
        let hour = document.querySelector('.hour');
        let minute = document.querySelector('.minute');
        let second = document.querySelector('.second');
        let inputTime = +new Date('2022-5-1 24:00:00');

        function countDown() {
            let nowTime = +new Date();
            let times = (inputTime - nowTime) / 1000;
            let h = parseInt(times / 60 / 60 % 24);
            h = h < 10 ? '0' + h : h;
            hour.innerHTML = h;
            let m = parseInt(times / 60 % 60);
            m = m < 10 ? '0' + m : m;
            minute.innerHTML = m;
            let s = parseInt(times % 60);
            s = s < 10 ? '0' + s : s;
            second.innerHTML = s;
        }

        setInterval(countDown, 1000);
    </script>
</body>

</html>

题目练习
https://www.nowcoder.com/exam/oj/ta?page=1&tpId=290&type=290
1、小飞机

image.png

console.log("     **     "+"\n"+"     **     "+"\n"+"************"+"\n"+"************"+"\n"+"    *  *    "+"\n"+"    *  *    ");

涉及：console.log()，字符串拼接，换行 \n
应用场景：
a.console.log()打印排查问题，读懂代码逻辑
eg:console.log('数据接口data',data)
debugger

练习

输入描述：
输入一个浮点数
输出描述：
输出一个浮点数，保留三位小数

console.log(parseFloat(readline()).toFixed(3))

let str = readline();
function f1(str){
    const str1 = str.toString()
    const idx = str1.indexOf('.')
    let first = parseFloat(str1.substring(0,idx+4))
    const char1 = parseFloat(str1.charAt(idx+4))
    if(char1>4){
        first = ((first*1000 + 1)/1000).toFixed(3)
    }
    console.log(first)
}
f1(str)

2.字符串反转

let str='123456';
str.split('').reduceRight((prev,curr)=>prev+curr)

先转换为数组

str.split('').reverse().join('')

3.数组去重

return Array.from(new Set(array))

Array.from
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Array/from
new Set()
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Set

好玩的~

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