How to judge time in JavaScript

JavaScript is a client-based scripting language commonly used in web development. In JavaScript, we often need to process and judge date and time. This article will briefly introduce how to judge time in JavaScript.

1. Get the current time

In JavaScript, we can use the Date() method to get the current date and time. As shown below:

var now = new Date(); //获取当前时间

This method returns a Date object and contains the current date and time information.

2. Create a specific time

If we need to create a specific time, we can use new Date(year, month, day, hour, minute, second) method. Where year represents the year, month represents the month (0 represents January, 11 represents December), day represents the date, hour represents hours, minute represents minutes, and second represents seconds. As shown below:

var specificDate = new Date(2022, 9, 1, 12, 0, 0); //创建一个特定的日期时间

3. Judge the size of two times

In JavaScript, we can judge the size of two times by comparing the number of milliseconds in the two times. . As shown below:

var date1 = new Date(2022, 9, 1, 12, 0, 0); 
var date2 = new Date(2022, 9, 2, 12, 0, 0);

if(date1.getTime() < date2.getTime()){
    console.log("date1 is earlier than date2");
}else{
    console.log("date2 is earlier than date1");
}

4. Determine whether a time is within the range of another time

In JavaScript, we can use getTime() The method gets the milliseconds of a time and then compares whether the milliseconds of that time are within the range of another time. For example, to determine whether a time is within a certain day, you can use the following method:

var date = new Date(2022, 9, 1, 12, 0, 0); //需要判断的时间
var startDate = new Date(2022, 9, 1, 0, 0, 0); //开始时间
var endDate = new Date(2022, 9, 2, 0, 0, 0); //结束时间

if(date.getTime() >= startDate.getTime() && date.getTime() < endDate.getTime()){
    console.log("date is in the range of the day");
}else{
    console.log("date is not in the range of the day");
}

5. Get the various parts of the time

In JavaScript, we can use getYear()、getFullYear()、getMonth()、getDate()、getDay()、 Methods such as getHours(), getMinutes() and getSeconds() obtain various parts of a time. For example, to get the year and month of the current time, you can use the following method:

var now = new Date();
var year = now.getFullYear(); //获取当前年份
var month = now.getMonth() + 1; //获取当前月份，需要加 1，因为月份从 0 开始计数

console.log(year + "-" + month);

6. Other commonly used methods

In addition to the above methods, there are some other commonly used times in JavaScript Processing methods, such as converting time format, adding and subtracting time, etc.

(1) Convert time format

We can use toLocaleDateString(), toLocaleTimeString() and toLocaleString() Method to convert a time object into string format. For example:

var now = new Date();
var dateString = now.toLocaleDateString(); //获取当前时间的日期部分，返回格式类似于 2022/10/12
var timeString = now.toLocaleTimeString(); //获取当前时间的时间部分，返回格式类似于 12:00:00
var dateTimeString = now.toLocaleString(); //获取当前时间的完整格式，返回格式类似于 2022/10/12 上午 12:00:00

(2) Time addition and subtraction

You can use setFullYear(), setMonth(), setDate( in JavaScript ), setHours(), setMinutes() and setSeconds() and other methods to perform time addition and subtraction operations. For example:

var now = new Date();
now.setFullYear(now.getFullYear() + 1); //将当前时间加一年
now.setMonth(now.getMonth() + 1); //将当前时间加一个月

The above are common time processing and judgment methods in JavaScript. In actual development, we can choose different methods according to specific needs.

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