How to display prime numbers in separate rows in JavaScript

JavaScript is a popular programming language that can be used to create various types of websites and applications. In JavaScript, a prime number is a positive integer that is only divisible by 1 and itself. When we need to display prime numbers on a web page, sometimes we need to display these numbers in separate lines for readability and beauty. This article will introduce how to display prime numbers in separate rows in JavaScript.

1. Judge prime numbers

To determine whether a number is prime in JavaScript, you can use the following code:

function isPrime(num) {
    for(let i = 2; i < num; i++) {
        if(num % i === 0) {
            return false;
        }
    }
    return num !== 1;
}

This code will loop through from 2 to For all numbers between num-1, check whether it is divisible by num. If it is divisible, it means that num is not a prime number and returns false. Otherwise, continue looping. Finally, if num is not equal to 1, it means it is a prime number and returns true.

2. Display prime numbers in separate lines

Generally, we will use an array to store the prime numbers we want to display. This array can be dynamically added with prime numbers in a loop. Next, we need a counter to count how many prime numbers are displayed in the current line. When the counter reaches the specified value, we need to display the prime number on a new line. The following code implements this function:

let primes = []; // 存储素数的数组
let rowNum = 10; // 每行显示的素数个数
let count = 0; // 当前行已经显示的素数个数

for(let i = 1; i <= 100; i++) {
    if(isPrime(i)) {
        primes.push(i); // 将素数添加到数组中
        count++; // 计数器加1
        if(count === rowNum) { // 如果当前行已经显示了rowNum个素数
            document.write("<br>"); // 换行
            count = 0; // 计数器清零
        }
    }
}

document.write(primes.join(", "));

In this example, we assume that each line displays up to 10 prime numbers. In the loop, if the current number is prime, add it to the array and increment the counter. If the counter is equal to 10, it means that 10 prime numbers have been displayed on the current line and need to be displayed on a new line. We use document.write("
") to wrap the line, clear the counter, and continue the loop.

Finally, we display all the prime numbers on the web page and use the primes.join(", ") function to convert the elements in the array into comma-separated strings.

3. Further optimization

The above code can realize the function of displaying prime numbers in separate lines, but sometimes we need to adaptively display prime numbers according to the width of the current screen. In this case, we need to dynamically calculate the number of prime numbers displayed in each row. Here's a simple example:

let screenWidth = window.innerWidth; // 获取屏幕宽度
let rowNum = Math.floor(screenWidth / 80); // 根据屏幕宽度计算每行显示的素数个数
let count = 0; // 当前行已经显示的素数个数

In this example, we assume that each prime on the screen is 80 pixels wide. We can use window.innerWidth to get the screen width, and then calculate the number of prime numbers displayed in each line based on the screen width. Finally, we use the count variable to record the number of prime numbers displayed on the current line and wrap the line as needed.

Summary

The line-by-line display of prime numbers in JavaScript requires judging the prime numbers and dynamically calculating the number of prime numbers displayed in each line. Through the above code implementation, we can easily display prime numbers on the web page and adaptively adjust the number of prime numbers displayed in each line as needed, making the web page more beautiful and easier to read.

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