Knowing calculate prime factors for a number is an important skill taught in high school mathematics. The Fundamental Theorem of Arithmetic states that non-prime positive integers can always be produced from the multiplication of its prime factors. A prime number has only two factors, itself and 1. You can use JavaScript code to create an algorithm that searches for a number's through repeated division, looking for factors that are prime.
Instructions
1. Open your HTML source file in a text editor, such as Windows Notepad.
2. Place the code "" in the "" section of your HTML file.
3. Create a JavaScript function that determines if a number is prime or not by adding the code:
"function isprime(x) { if (x % 2 == 0) { return false; } var endvalue = Math.ceil(Math.sqrt(x)); for (a = 3; a <= endvalue; a += 2) { if ((x % a) == 0) return false; } return true; }."
The function keeps dividing the input by smaller numbers to see whether any divide evenly into it, returning true if it finds any factors and false otherwise. This function will be called when a factor is found in the main function, to determine whether it's a prime factor or not.
4. Add a JavaScript function that calculates the prime factors of a number with the following code:
"function calcprimefactors (form) { n = form.n.value; var found = false; document.write(n + ' = '); if (n % 2 == 0) { document.write('2 '); found = true; } for (div = 3; div <= n/2; div++) { if ((n % div) == 0) { if (isprime(div) == true) { document.write(div + ' '); found = true; } } } if (found == false) { document.write('prime'); } }."
The function searches for factors by using a loop to divide the input by numbers smaller than itself, checking each factor to see whether it's prime or not. It then outputs a list of the prime factors. If you want to directly pass a number to the function, replace the "form" parameter with "n" and remove the "n = form.n.value;" line of code.
5. Place a "" tag after the JavaScript functions.
6. Create a form in the body of your HTML file where a visitor can input a number by adding the code:
" ."
When the visitor types in a number and clicks the button the prime factor function will run, using the number typed in the form as its input.
7. Save the HTML file and load it on your server.
Tags: prime factors, HTML file, your HTML, adding code, code function, document write