Numbers programs

 1. Write a program to find the sum of natural numbers?

function addUpToNumber(n) {
    var total = 0;
    for(let i = 1; i <= n; i++) {
        total = total + i;
    }
    return total;
} 
 
addUpToNumber(4);


2. Write a program to find the sum of natural numbers without loop?

function addUpToNumber(n) {
    return n * (n+1)/2
}

addUpToNumber(4);

3. Write a program to find the sum of even numbers?

function sumOfFirstEvenNumbers(n) {
    return n * (n+1)
} 
 
sumOfFirstEvenNumbers(4); 

4. Write a program to find the sum of even numbers in a range? 

function sumOfEvenNumbersBetweenRange(i, n) {
    var result = 0;
    for (let index = i; index <= n; index++) {
        if(index % 2 == 0) {
            result = result + index;
            console.log(result);
        }
    }
    return result;
} 
 
sumOfEvenNumbersBetweenRange(1, 4);

5. Write a program to find a given number is even or odd?

function checkNumberType(n) {
    if(n == 0) {
        console.log("Neither even nor odd.");
        return;
    }
    if(n%2 == 0) {
        console.log("even number !!");
    } else {
        console.log("odd number !!");
    }
}

checkNumberType(7); // odd number

           checkNumberType(-6);  // even number(All integers which are divisible by 2 are even numbers)

6. Write a program to find the sum of odd numbers?

function sumOfOddNumbers(n) {
    return n*n;
}

sumOfOddNumbers(4);

7. Write a program to find the sum of numbers in a string?

 function numberAdd(str){
var strArr = str.split(""), result=0;
for(i=0;i<strArr.length;i++){
if(!isNaN(strArr[i])){
result = result + parseInt(strArr[i]);
}
}
return result;
} 
 
console.log(numberAdd("123sdfsdf1.5"));

8. Write a program to swap numbers without using a third variable?

function swapNumbers(n1, n2) {
    n1 = n1 + n2;
    n2 = n1 - n2;
    n1 = n1 - n2
    console.log(n1, n2);
}

swapNumbers(4,7); 

8. Write a program to find a given number or prime number or not?

 function isPrimeNumber(num){
    var isPrime = true;
if(num > 1) {
        for (let index = 2; index < num; index++) {
            if(num % index == 0) {
                isPrime = false;
                break;
            }
        }
    } else {
        isPrime = false;
    }
    if(isPrime) {
        console.log("prime number");
    } else {
        console.log("not a prime number");
    }
}

console.log(isPrimeNumber(6));



 

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