How to determine leap year in javascript

How to judge a leap year in JavaScript

A leap year refers to a year in the Gregorian calendar when the remainder is zero when divided by 4 but not zero when divided by 100 or when divided by 400 the remainder is zero. Because there are 366 days in a leap year, special date-related issues need to be handled in programming. JavaScript, as a common programming language, also provides a method to determine leap years.

1. Use if statement

Use if statement to determine whether the given year is a leap year. The specific implementation is as follows:

function isLeapYear(year) {
    if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
        return true;
    } else {
        return false;
    }
}

In this function, First determine whether it is divisible by 4 and not divisible by 100, or whether it is divisible by 400. If it is divisible, it means it is a leap year and returns true; otherwise, it is not a leap year and returns false.

2. Use the ternary operator

Another way to determine leap years is to use the ternary operator in JavaScript. The code is as follows:

function isLeapYear(year) {
    return (year % 4 == 0 && year % 100 != 0) || year % 400 == 0 ? true : false;
}

This method has the same implementation principle as the if statement, except that the ternary operator is used instead of the if statement.

3. Using Date Object

The Date object in JavaScript also provides a method to determine leap years. You can get the year of a given date by calling the getYear() method in the Date object. . The code is as follows:

function isLeapYear(year) {
    var date = new Date(year, 1, 29);
    return date.getMonth() == 1;
}

In this function, instantiate a Date object, pass in the year as a parameter, and then set the date to February 29. If the month of the date is 2, it means it is a leap year.

It should be noted that when using a Date object to determine a leap year, the year must be passed in, and the month must be February, otherwise it will not be determined correctly.

Summary

The above are three ways to determine leap years in JavaScript. For the judgment of leap year, we can choose the appropriate method according to the specific situation. Using if statements and ternary operators can easily and quickly implement leap year judgment, while using Date objects can handle date-related issues more flexibly, but of course more code is required to implement it. In actual development, you can choose which method to use based on specific needs.

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