I have this code that finds all the prime numbers between 2 values, but how do i change it to find only the first one?
e.g. 33 and 147 = 37
let a, b, i, j, primo;
a = window.prompt("Numero minimo: ");
b = window.prompt("Numero maximo: ");
console.log("Numeros primos entre " + a + " e " + b << " é: ");
for (i = a; i <= b; i++) {
if (i == 1 || i == 0)
continue;
primo = 1;
for (j = 2; j < i; ++j) {
if (i % j == 0) {
primo = 0;
break;
}
}
if (primo == 1)
document.write(i," ");
}
You can extend the final if statement with this:
if (primo == 1) {
document.write(i, " ");
break;
}
break allows you to exit the for loop. You can learn more here: https://www.w3schools.com/js/js_break.asp
let a, b, i, j, primo;
a = window.prompt("Numero minimo: ");
b = window.prompt("Numero maximo: ");
console.log("Numeros primos entre " + a + " e " + b << " é: ");
for (i = a; i <= b; i++) {
if (i == 1 || i == 0)
continue;
primo = 1;
for (j = 2; j < i; ++j) {
if (i % j == 0) {
primo = 0;
break;
}
}
if (primo == 1) {
document.write(i, " ");
break;
}
}That would be the algorithm for find the first prime in a array.
function makeArr(start, end) {
end++
return Array.from({length: (end-start)}, (v, k) => k+start)
}
isPrime = num => {
for(let i = 2, s = Math.sqrt(num); i <= s; i++)
if(num % i === 0) return false;
return num > 1;
}
nums = makeArr(33,147);
r = nums.filter(n => isPrime(n))
console.log(r[0])Wrapped in a function example
function getFirstPrimeNumber(s, e) {
const start = parseInt(s);
let end = parseInt(e);
end++;
const _a= Array.from({length: (end-start)}, (v, k) => k+start)
const isPrime = num => {
for(let i = 2, s = Math.sqrt(num); i <= s; i++)
if(num % i === 0) return false;
return num > 1;
}
const primes = _a.filter(n => isPrime(n));
return primes[0];
}
const a = window.prompt("Numero minimo: ");
const b = window.prompt("Numero maximo: ");
const r = getFirstPrimeNumber(a,b)
console.log('result', r);