// 素数:除了1和它本身没有其他因数
function judgePrimeNum(num) {
let str = ''
if (!isNaN(num)) {
if (num === 1) {
str = '1既不是素数也不是合数'
} else if (num === 2) {
str = "2是素数"
} else {
for (let i = 2; i < num; i++) {
if (num % i === 0) {
str = '不是素数'
break
} else {
str = `${num}是素数`
}
}
}
} else {
str = "非数字"
}
return str
}
const numStr = judgePrimeNum('1a')
console.log(numStr)