Prime: Also known as prime numbers, in natural numbers greater than 1, there are no other factors except 1 and itself.
That is, the number that can only be divisible by 1 and itself is a prime number. This is a question that I often do when I get started with programming.
// Determine whether a number is a prime number (prime number). (A number that can only be divisible by 1 and itself, or: except 1 and itself, no other number can be divisible by it)//Method 1:function test(){
//1, input var num = parseInt(("num").value);//9
//2. Business logic for(var i=2;i<=num-1;i++){//i=7 num=7
if(num%i==0){
break;
}
}
if(i>num-1){
alert(num+"It's a prime number");
}else{
alert(num+"It's a composite number");
}
}
//Method 2:function test(){
//1, input var num = parseInt(("num").value);//9
//2. Business logic var isSu=true;//isSu: indicates whether it is a prime number; assuming it is a prime number; for(var i=2;i<=num-1;i++){
if(num%i==0){
isSu = false;
break;
}
}
if(isSu==true){
alert(num+"It's a prime number");
}else{
alert(num+"It's a composite number");
}
}//Method 3:function test(){
//1, input var num = parseInt(("num").value);//9
//2. Business logic var count=0;//Record the number of divisors for(var i=2;i<=num-1;i++){//
if(num%i==0){
count++;
break;
}
}
if(count==0){
//3, output alert(num+"It's a prime number");
}else{
alert(num+"It's a composite number");
}
}Summarize
This is the end of this article about how to judge whether a number is a prime number in JS. This is the end. For more related JS. content, please search my previous article or continue browsing the related articles below. I hope everyone will support me in the future!