Trouble with Sum Array Function

Question

Trouble with Sum Array Function

I've encountered an issue while trying to calculate the sum of a dynamic array. Instead of adding up the numbers, they are just being displayed next to each other. I attempted to sum 1+2+3+4+5, but the output shows as 012345 instead of 15.

let userInput = -1;
const totalInputs = [];
let sum = 0;
let j = 0;

while(userInput !== 999) {
    userInput = window.prompt("Enter a test score, or 999 to end the program");

    if(userInput <= 100 && userInput >= 0) {
        totalInputs[j] = userInput;
        j++;
    }
}

$("lastScore").value = totalInputs[j-1];

for(let i = 0; i < totalInputs.length; i++) {
    sum += totalInputs[i];
}

$("sumScores").value = sum;

When the prompt appears, I input 1, 2, 3, 4, 5 while pressing enter between each value, followed by 999 to end the prompt. However, the result is 012345 instead of the expected 15. I have tried various solutions but cannot figure out why it behaves this way. The $ function simply returns

window.document.getElementById(theId);

javascript arrays

Answer 1

Answer №1

Let's make a simple change in the code below:

for(var i = 0; i < totalInputs.length; i++)
{
    sum += +totalInputs[i]; //this makes sure the string is coerced to a number.
}

In JavaScript, converting a = "1" to a = 1 can be easily done by using the unary plus operator like so: a = +a. This kind of coercion is a unique feature of JavaScript.

The reason you are experiencing this issue is because the user input from the prompt box is always treated as a string.

Answer 2

Let's make a simple change in the code below:

for(var i = 0; i < totalInputs.length; i++)
{
    sum += +totalInputs[i]; //this makes sure the string is coerced to a number.
}

In JavaScript, converting a = "1" to a = 1 can be easily done by using the unary plus operator like so: a = +a. This kind of coercion is a unique feature of JavaScript.

The reason you are experiencing this issue is because the user input from the prompt box is always treated as a string.

Answer 3

Answer №2

Initially, the script contains numerous typos which made it challenging to get it to function properly.

Here's the breakdown: when a prompt is used, the browser stores the input as a string. If you try to add the string at index 0 with the string at index 1, you will end up concatenating them instead of adding as numbers. To resolve this issue, you can utilize the parseInt function.

var userInput = -1;
var totalInputs = [];
var sum = 0;
var j = 0;

while(userInput != 999)
{
  userInput = window.prompt("Enter a test score, or 999 to end the program");

  if(userInput <= 100 && userInput >= 0)
  {
    totalInputs[j] = userInput;
    j++;
  }
}

$("lastScore").value = totalInputs[j-1];

for(var i = 0; i < totalInputs.length; i++)
{
  sum += parseInt(totalInputs[i]);
}

$("sumScores").value = sum;

By following these steps, the script should now work correctly. Take note of the ParseInt method within the for loop, converting the string into an Integer for proper addition.

To enhance the code further, consider storing the inputs as Integers initially rather than casting them during summation. Update the prompt section from:

userInput = window.prompt("Enter a test score, or 999 to end the program");

To:

userInput = parseInt(window.prompt("Enter a test score, or 999 to end the program"));

This adjustment allows you to remove the parseInt function from the for loop. Hence, modify the line:

// sum += parseInt(totalInputs[i]);
sum += totalInputs[i];

Answer 4

Initially, the script contains numerous typos which made it challenging to get it to function properly.

Here's the breakdown: when a prompt is used, the browser stores the input as a string. If you try to add the string at index 0 with the string at index 1, you will end up concatenating them instead of adding as numbers. To resolve this issue, you can utilize the parseInt function.

var userInput = -1;
var totalInputs = [];
var sum = 0;
var j = 0;

while(userInput != 999)
{
  userInput = window.prompt("Enter a test score, or 999 to end the program");

  if(userInput <= 100 && userInput >= 0)
  {
    totalInputs[j] = userInput;
    j++;
  }
}

$("lastScore").value = totalInputs[j-1];

for(var i = 0; i < totalInputs.length; i++)
{
  sum += parseInt(totalInputs[i]);
}

$("sumScores").value = sum;

By following these steps, the script should now work correctly. Take note of the ParseInt method within the for loop, converting the string into an Integer for proper addition.

To enhance the code further, consider storing the inputs as Integers initially rather than casting them during summation. Update the prompt section from:

userInput = window.prompt("Enter a test score, or 999 to end the program");

To:

userInput = parseInt(window.prompt("Enter a test score, or 999 to end the program"));

This adjustment allows you to remove the parseInt function from the for loop. Hence, modify the line:

// sum += parseInt(totalInputs[i]);
sum += totalInputs[i];

Answer 5

Answer №3

Although one answer has already been marked as correct, I'd like to offer my own perspective. The answers provided above may work in certain cases, but they are prone to bugs due to the unreliable nature of user input.

@Luis's answer is effective, but have you considered inputting alphanumeric characters like 1bs64s? When parsed, it returns just the number 1. This unexpected behavior could be confusing for users, even though it might be acceptable to you. It's crucial to consider the user's perspective when allowing alphanumeric inputs.

Here is an explanation of why this issue occurs if you're curious:

When parseInt encounters a non-numeric character in the specified radix, it disregards that character and all following ones, returning the integer value parsed up to that point. Leading and trailing spaces are permitted, and numbers are truncated to integers.

Simply setting the radix base to 10 doesn't fully resolve the problem, as demonstrated by @Programmer's scenario with numbers between 0 and 100 still being accepted.

@Pbd's answer also experiences similar issues, coercing strings into numbers without proper validation.

// Without proper validation, this condition allows `1e1` to be stored in an array.
if("1e1" <= 100 && "1e1" >= 0) // evaluates to true!

Due to dynamic typing, the output differs upon summation.

var sum = 0;
sum += totalInputs[i] // assuming totalInputs[i] returns `1e1`
console.log(sum);     // outputs "01e1".

There are various strategies for validating inputs securely, but in my opinion, trimming user input, converting strings to numbers, and validating convertibility into integers is a reliable approach.

userInput = window.prompt("Enter a test score, or 999 to end the program").trim(); // or userInput = userInput.trim();

var convertedInput = +userInput;
var isNumber = convertedInput == userInput; // checking equality "1" == 1
if(userInput && isNumber && convertedInput >= 0 && convertedInput <= 100)
    totalInputs[j] = convertedInput;

To simplify the summation process, consider using reduce.

var sum = totalInputs.reduce(function(pv, cv) { return pv + cv; }, 0);

Alternatively, with arrow functions from ES6, the code becomes even more concise:

var sum = totalInputs.reduce((pv, cv) => pv+cv, 0);

Credit goes to @Chaos's answer. I haven't tested reduce performance across different browsers yet.

Javascript can be quite enjoyable! :)

Answer 6

Although one answer has already been marked as correct, I'd like to offer my own perspective. The answers provided above may work in certain cases, but they are prone to bugs due to the unreliable nature of user input.

@Luis's answer is effective, but have you considered inputting alphanumeric characters like 1bs64s? When parsed, it returns just the number 1. This unexpected behavior could be confusing for users, even though it might be acceptable to you. It's crucial to consider the user's perspective when allowing alphanumeric inputs.

Here is an explanation of why this issue occurs if you're curious:

When parseInt encounters a non-numeric character in the specified radix, it disregards that character and all following ones, returning the integer value parsed up to that point. Leading and trailing spaces are permitted, and numbers are truncated to integers.

Simply setting the radix base to 10 doesn't fully resolve the problem, as demonstrated by @Programmer's scenario with numbers between 0 and 100 still being accepted.

@Pbd's answer also experiences similar issues, coercing strings into numbers without proper validation.

// Without proper validation, this condition allows `1e1` to be stored in an array.
if("1e1" <= 100 && "1e1" >= 0) // evaluates to true!

Due to dynamic typing, the output differs upon summation.

var sum = 0;
sum += totalInputs[i] // assuming totalInputs[i] returns `1e1`
console.log(sum);     // outputs "01e1".

There are various strategies for validating inputs securely, but in my opinion, trimming user input, converting strings to numbers, and validating convertibility into integers is a reliable approach.

userInput = window.prompt("Enter a test score, or 999 to end the program").trim(); // or userInput = userInput.trim();

var convertedInput = +userInput;
var isNumber = convertedInput == userInput; // checking equality "1" == 1
if(userInput && isNumber && convertedInput >= 0 && convertedInput <= 100)
    totalInputs[j] = convertedInput;

To simplify the summation process, consider using reduce.

var sum = totalInputs.reduce(function(pv, cv) { return pv + cv; }, 0);

Alternatively, with arrow functions from ES6, the code becomes even more concise:

var sum = totalInputs.reduce((pv, cv) => pv+cv, 0);

Credit goes to @Chaos's answer. I haven't tested reduce performance across different browsers yet.

Javascript can be quite enjoyable! :)

Trouble with Sum Array Function

Answer №1

Answer №2

Answer №3

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