Ndtyjky

Ask user to enter a number. Then ask the user to enter a number bigger than the first number. Calculate a value that is the sum of all the numbers from the first number to the second number including the end points. For example, if the user enters 5 and 10 then calculate the total of 5 + 6 + 7 + 8 + 9 + 10. Display the results. MUST USE A WHILE LOOP

This is what I have so far. I can't seem to get the sum to be correct. If I enter the numbers from the example above, I get 49 instead of 45. I understand where I went wrong and why it is 49 based on my code but can't figure out how to make it correct.

// declare constants

const INITIAL_VALUE = 0;

const COUNTER_VALUE = 1;



// declare variables

var number1;

var number2;

var sum;

var counter;

var difference;

var middlePoint;

var middlePointSum;



// assigning values

sum = INITIAL_VALUE;

difference = INITIAL_VALUE;

counter = COUNTER_VALUE;

middlePoint = COUNTER_VALUE;

middlePointSum = INITIAL_VALUE;



// prompt user to enter two numbers

number1 = prompt("Enter first number: ");

number2 = prompt("Enter a number bigger than first number: ");



// convert user input into numbers

number1 = Number(number1);

number2 = Number(number2);



// display number1

document.write(number1);

difference = number2 - number1;

middlePoint += number1;



while (counter < difference) {

   document.write(" + " + middlePoint);

   middlePoint = middlePoint + 1;

   counter++;

   middlePointSum += middlePoint;

}



// calculate the sum

sum = number1 + middlePointSum + number2;

 

// display number1, middle points, number2, and sum

document.write(" + " + number2 + " = " + sum);

Welcome to StackOverflow!

The cause of error is at this part of the code

while (counter < difference) {

    document.write(" + " + middlePoint);

    middlePoint = middlePoint + 1; // you are already increasing the middlePoint number

    counter++;

    middlePointSum += middlePoint;

}

Therefore, the sum is always over by the number of counter - 1. What you should have done, is execute middlePointSum += middlePoint; first before increasing the value of middlePoint and counter.

while (counter < difference) {

    document.write(" + " + middlePoint);

    middlePointSum += middlePoint;

    middlePoint = middlePoint + 1;

    counter++;

}

This code should work for you. Variabel sum should contain your desired sum.

var sum = 0;

var firstNumber = 0;

var secondNUmber = 0;

var firstNumberStr = '';

var secondNUmberStr = '';



// prompt user to enter two numbers

firstNumberStr = prompt("Enter first number: ");



while(isNaN(firstNumberStr)){

    firstNumberStr = prompt("Enter Correct first number: ");

}



secondNUmberStr = prompt("Enter a number bigger than first number: ");



while(isNaN(secondNUmberStr) || parseInt(firstNumberStr) >= parseInt(secondNUmberStr)){

    secondNUmberStr = prompt("Enter a number bigger than first number: ");

}



firstNumber = parseInt(firstNumberStr); 

secondNUmber = parseInt(secondNUmberStr);



while(firstNumber <= secondNUmber){

    sum += firstNumber;

    firstNumber++

}

You did a very small mistake in the code . The bug is in while loop.

 while (counter < difference) {

        document.write(" + " + middlePoint);

        middlePoint = middlePoint + 1;

        counter++;

        middlePointSum += middlePoint;

    }

you are incrementing the middlepoint before middlePointSum is Calculated. It should be incremented after calculating the middlePointSum.

while (counter < difference) {

    document.write(" + " + middlePoint);

    counter++;

    middlePointSum += middlePoint;

    middlePoint = middlePoint + 1;

}

Your middlePointSum is starting from 1 intead of 0 so you got: 5 + (7 + 8 + 9 + 10) + 10 to fix your code set middlePointSum to INITIAL_VALUE

For simplification just ignore the difference between the numbers, increment number1 until you reach number 2

var number1 = prompt("Enter first number: ");

var number2 = prompt("Enter a number bigger than first number: ");

var incNumber;

var strResult = ;



number1 = incNumber = Number(number1);

// use incNumber if you need to preserve number1 value or just use number 1 value instead

number2 = Number(number2);



var sum = 0;

while(incNumber <= number2) {

  strResult.push(incNumber);

  sum += incNumber++;

  // this means add incNumber to sum then increment it by 1

}



document.write(`${strResult.join(' + ')} = ${sum}`);

One problem is that your middlePointSum does not take into account the first number after the number1, for example, the 6 in your example. Another problem is that your counter < difference test is inaccurate - you would have to iterate until counter + 1 < difference:

// declare constants

const INITIAL_VALUE = 0;

const COUNTER_VALUE = 1;



// declare variables

var number1;

var number2;

var sum;

var counter;

var difference;

var middlePoint;

var middlePointSum;



// assigning values

sum = INITIAL_VALUE;

difference = INITIAL_VALUE;

counter = COUNTER_VALUE;

middlePoint = COUNTER_VALUE;

middlePointSum = INITIAL_VALUE;



// prompt user to enter two numbers

number1 = prompt("Enter first number: ");

number2 = prompt("Enter a number bigger than first number: ");



// convert user input into numbers

number1 = Number(number1);

number2 = Number(number2);



// display number1

document.write(number1);



difference = number2 - number1;

middlePoint += number1;



middlePointSum = middlePoint;

while (counter + 1 < difference) {

  document.write(" + " + middlePoint);

  middlePoint = middlePoint + 1;

  counter++;

  console.log(middlePointSum);

  middlePointSum += middlePoint;

}



// calculate the sum

sum = number1 + middlePointSum + number2;



// display number1, middle points, number2, and sum

document.write(" + " + number2 + " = " + sum);

But this seems far, far more complicated than it needs to be - why not simply iterate from number1 to number2, adding to sum along the way?

const number1 = Number(prompt("Enter first number: "));

const number2 = Number(prompt("Enter a number bigger than first number: "));

document.write(number1);

let sum = number1;

for (let i = number1 + 1; i <= number2; i++) {

  sum += i;

  document.write(' + ' + i);

}

document.write(' = ' + sum);

Or, create an array of the numbers, join by plus signs, and calculate the sum with reduce:

const number1 = Number(prompt("Enter first number: "));

const number2 = Number(prompt("Enter a number bigger than first number: "));



const nums = Array.from(

  { length: number2 - number1 + 1 },

  (_, i) => i + number1

);

const sum = nums.reduce((a, b) => a + b);

document.write(nums.join(' + ') + ' = ' + sum);

var num1 = Number(prompt("Enter a number"));

var num2 = Number(prompt("Enter a larger number"));





document.write(num1 + "+" + num2 + "=" + (num1+num2));







// now lets find the sum of numbers between these two numbers.

document.write("<br>");  // new line



var counter = num1;   // we will start countring from the smaller number

var sum = 0;



//keep looping until we reach the bigger number (num2)

while(counter<=num2) {

  sum += counter;

  // print the current number

  document.write(counter);

  //print a plus sign

  if(counter<num2) { 

    // only put a (plus sign) if we are not yet reached num2

    document.write("+"); 

   }

   

   //increment to control the loop

  counter ++;

  

}





//finally put the result

document.write("=" + sum);

You are setting counter to the constant COUNTER_VALUE which is 1.

Then, in your program, you are entering 5 and 6 as input. The difference is 6-5 which is 1.

Your while loop has a condition to only execute when counter<difference . In your case, counter=1 and difference=1. This means that they are equal, and thus, the loop will not execute.

I hope this sheds light on what needs to be done from your side to fix this bug.