JavaScript获取当前时间

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div></div>
</body>
</html>
<script type="text/javascript">
    /**
     * 获取当前时间
     */
    function getCurrentDate() {
        let currentDate = new Date();
        let fullYear = currentDate.getFullYear();// 获取当前年份(4位)
        console.log(fullYear);
        let month = currentDate.getMonth();// 获取当前月份(0-11,0代表1月)
        console.log(month);
        let date = currentDate.getDate();// 获取当前日(1-31)
        console.log(date);
        let day = currentDate.getDay();// 获取当前星期X(0-6,0 代表星期天)
        console.log(day);
        let time = currentDate.getTime();// 获取当前时间(从1970.1.1开始的毫秒数)
        console.log(time);
        let hours = currentDate.getHours();// 获取当前小时数(0-23)
        console.log(hours);
        let minutes = currentDate.getMinutes();// 获取当前分钟数(0-59)
        console.log(minutes);
        let seconds = currentDate.getSeconds();// 获取当前秒数(0-59)
        console.log(seconds);
        let milliseconds = currentDate.getMilliseconds();// 获取当前毫秒数(0-999)
        console.log(milliseconds);
        let localeDateString = currentDate.toLocaleDateString();// 获取当前日期
        console.log(localeDateString);
        let localeTimeString = currentDate.toLocaleTimeString();// 获取当前时间
        console.log(localeTimeString);
        let localeString = currentDate.toLocaleString();// 获取当前日期与时间
        console.log(localeString);
    }
	// 调用函数
    getCurrentDate();
</script>

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JavaScript获取当前时间的一年前时间

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div></div>
</body>
</html>
<script type="text/javascript">
    /**
     * 获取当前时间的一年前时间
     */
    function getYearAgo() {
        const currentDate = new Date();
        currentDate.setFullYear(currentDate.getFullYear() - 1)
        let localeString = currentDate.toLocaleString();
        console.log("当前时间的一年前时间:" + localeString);
    }
	// 调用函数
    getYearAgo();
</script>

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JavaScript获取当前时间的半年前时间

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div></div>
</body>
</html>
<script type="text/javascript">
    /**
     * 获取当前时间的半年前时间
     */
    function getYearHalf() {
        const currentDate = new Date();
        currentDate.setMonth(currentDate.getMonth() - 6);
        // currentDate.setDate(currentDate.getDate() -1)
        let localeString = currentDate.toLocaleString();
        console.log("当前时间的半年前时间:" + localeString);
    }
	// 调用函数
    getYearHalf();
</script>


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JavaScript获取当前时间至一年前的所有年月

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div></div>
</body>
</html>
<script type="text/javascript">
    /**
     * 获取当前时间至一年前所有的年月
     * @returns {*[]}
     * 如输出 ["2022-07", "2022-08", "2022-09", "2022-10", "2022-11", "2022-12", "2023-01", "2023-02", "2023-03", "2023-04", "2023-05", "2023-06", "2023-07"]
     */
    function getLastMonth() {
        let result = [];
        for (let i = 0; i < 13; i++) {
            const currentDate = new Date();
            currentDate.setDate(1);// 将当前时间的日期设置成第一天
            let month = currentDate.getMonth() - i;
            currentDate.setMonth(month)
            let returnMonth = currentDate.getMonth() + 1;
            returnMonth = returnMonth < 10 ? "0" + returnMonth : returnMonth;//自定义输出日期的格式
            // result.push(currentDate.getFullYear() + "年" + returnMonth+"月");
            result.push(currentDate.getFullYear() + "-" + returnMonth);
        }
        return result;
    }

    let info = getLastMonth().reverse(); //反转
    console.log(info)
</script>

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JavaScript获取当前月第一天和最后一天

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div></div>
</body>
</html>
<script type="text/javascript">
    // 获取当前月第一天
    function getFirstDay() {
        const date = new Date();
        // 将当前时间的日期设置成第一天
        date.setDate(1);
        let y = date.getFullYear();
        let m = date.getMonth() + 1;
        // 月份补 0
        m = m < 10 ? '0' + m : m;
        let d = date.getDate();
        // 日期补 0
        d = d < 10 ? '0' + d : d;
        let firstDay = [y, m, d].join('-');
        return firstDay
    }

    console.log("获取当前月第一天:" + getFirstDay())

    // 获取当前月最后一天
    function getLastDay() {
        const date = new Date();
        let y = date.getFullYear();
        let m = date.getMonth() + 1;
        // 月份补 0
        m = m < 10 ? '0' + m : m;
        // new Date(y, m, 0) 获取当前月的最后一天,参数 0 代表上个月的最后一天
        let d = new Date(y, m, 0).getDate();
        // 日期补 0
        d = d < 10 ? '0' + d : d;
        let lastDay = [y, m, d].join('-');
        return lastDay
    }

    console.log("获取当前月最后一天:" + getLastDay())

    // 获取当前月第一天和最后一天
    function getFirstLastDay1(date) {
        let y = date.getFullYear();
        let m = date.getMonth() + 1;
        m = m < 10 ? '0' + m : m;
        // 设置为日期1号
        date.setDate(1);
        let firstDay = date.getDate();
        firstDay = firstDay < 10 ? '0' + firstDay : firstDay;
        let first = [y, m, firstDay].join('-');

        // 获取当前月的最后一天,参数 0 代表上个月的最后一天
        let lastDay = new Date(y, m, 0).getDate();
        let last = [y, m, lastDay].join('-');
        return first + " 至 " + last
    }

    console.log("起止日期:" + getFirstLastDay1(new Date()))

    // 获取当前月第一天和最后一天
    function getFirstLastDay2(dateString) {
        let year = Number(dateString.slice(0, 4));
        let month = Number(dateString.slice(4, 6));

        let date = new Date(year, month - 1);
        let y = date.getFullYear();
        let m = date.getMonth() + 1;
        m = m < 10 ? '0' + m : m;
        // 设置为日期1号
        date.setDate(1);
        let firstDay = date.getDate();
        firstDay = firstDay < 10 ? '0' + firstDay : firstDay;
        let first = [y, m, firstDay].join('-');

        // 获取当前月的最后一天,参数 0 代表上个月的最后一天
        let lastDay = new Date(year, month, 0).getDate();
        let last = [y, m, lastDay].join('-');
        return first + " 至 " + last
    }

    console.log("起止日期:" + getFirstLastDay2("202309"))

</script>

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