Prime Number

Enter a number and JavaScript can instantly tell you if it is a prime number or not. I wish I had this little gem to help me in my math classes years ago!

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JavaScript Source Code 3000: Calculator: Prime Number Simply click inside the window below, use your cursor to highlight the script, and copy (type Control-c or Apple-c) the script into a new file in your text editor (such as Note Pad or Simple Text) and save (Control-s or Apple-s). The script is yours!!!

<!-- TWO STEPS TO INSTALL PRIME NUMBER CALCULATOR: 1. Paste the coding into the HEAD of your HTML document 2. Put the last code into the BODY of your HTML document --> <!-- STEP ONE: Copy this code into the HEAD of your HTML document --> <SCRIPT LANGUAGE="JavaScript"> <! > <! > <!-- Begin function calculate(form) { var num=parseInt(form.number.value); if (isNaN(num) || num < 0) { form.result.value=(form.number.value + " is not a valid number! Try again!"); } if (num == 1 || num == 2) { form.result.value=(num + " is prime!"); } for (var i=2;i<num;i++) { if (num % i == 0) { var prime="yes"; form.result.value=(num + " is not prime. It is divisible by " + i + "."); break; } if (num % i != 0) var prime="no"; } if (prime == "no") form.result.value=(num + " is prime!"); } // End --> </SCRIPT> </HEAD> <!-- STEP TWO: Copy this code into the BODY of your HTML document --> <center> <form name=form> <h2>Prime Number Calculator</h2><p> Please enter a number:<br> <input type=text name=number size=7> <input type=button value="Calculate" onClick="calculate(this.form)"> <P> <input type=text name=result size=45 value=""> </form> </center> <!-- Script Size: 0.88 KB -->