How to multiply a constant array by a user input array?

Question

How do I apply my constant array by an array the user inputs and get the sum?

The user always enters 6 digits but constant is 5 digits

Example

[5, 7, 3, 5, 2] is my constant array that I am multiplying by

user enters 837465

turns into [8, 3,7,4,6,5] (but I want 5 to be ignored)

multiply by constant array(not including last element) and get sum:

(8*5)+ (3*7) + (7*3) + (4*5)+ (6*2) = 114

const arr = [5, 7, 3, 5, 2];
var arr2 = [];
var num = parseInt(document.getElementById("yourNumber").value); //input from .html

var sum = 0;
for (var i = 1; i< num.length; i++){  //var i = 1 b/c user always enters 6 digits, i feel this is wrong?
    arr2.push(parseInt(num[i]));
    sum += (arr2[i]*arr[i]);
}

console.log(sum);

i should go from 0 to arr.length. Make sure to check if your number has enough digits before the loop (>=arr.length). Also, you don't need to convert the value to integer, since you will be using each digit (i.e, each character) separately. Then, the operation is just sum+=arr[i]*num[i], you can access each character of a string as if it were an array. — Gabriel
– Gabriel, Commented Apr 2, 2020 at 23:29

ironCat · Accepted Answer · 2020-04-02 23:53:42Z

1

try use const input = '837465'.split('') or ready array const input = [8, 3, 7, 4, 6, 5] and reduce() method for summation array. reduce will work while there are elements in the original array

const array = [5, 7, 3, 5, 2]
const input = '837465'.split('')
//or 
// const input = [8, 3, 7, 4, 6, 5]

const summ = (input) => array.reduce((acum, rec, index) => acum + (rec * input[index]), 0)

console.log(summ(input))

answered Apr 2, 2020 at 23:53

ironCat

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1 Comment

ReaperSoon Over a year ago

Beautiful answer !

Maxqueue · Accepted Answer · 2020-04-02 23:36:00Z

0

Following works:

const arr = [5, 7, 3, 5, 2];
var num = document.getElementById("yourNumber").value; //input from .html

var sum = 0;
for (var i = 0; i< num.length-1; i++){  //var i = 1 b/c user always enters 6 
digits, i feel this is wrong?
    sum += (arr[i]*parseInt(num[i]));
}

console.log(sum);

answered Apr 2, 2020 at 23:36

Maxqueue

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Comments

Guest · Accepted Answer · 2020-04-02 23:36:41Z

0

You can do it imperatively using the legible for-of syntax -

const arr = [5, 7, 3, 5, 2]
const nums = [8, 3, 7, 4, 6, 5]

let result = 0

for (const [ key, value ] of Object.entries(arr))
  result = result + (value * nums[key])

console.log(result) // 114

Or you can do it declaratively using Array.prototype.reduce -

const arr = [5, 7, 3, 5, 2]
const nums = [8, 3, 7, 4, 6, 5]

const result =
  arr.reduce
    ( (sum, value, key) => sum + (value * nums[key])
    , 0
    )

console.log(result) // 114

answered Apr 2, 2020 at 23:36

Guest

1

Comments

Mohammad Jouza · Accepted Answer · 2020-04-03 01:51:28Z

Here is the answer (please click on Run code Snippet)

If you need any explanation, or this is not what you are asking about, please comment on my answer

function getTotal() {
  const arr = [5, 7, 3, 5, 2];
  var userNumbers = document.getElementById('yourNumber').value.split(''); 
  var sum = 0;
  //itreate over your array case it is short (or a condition to itreate over the shortest one)
  for (var i = 0; i < arr.length; i++) {
    sum += parseInt(userNumbers[i]) * arr[i];
  }

  console.log(sum);
  document.getElementById('answer').innerHTML ='Answer will be here: '+ sum;
}

<html>

<head>
  <title>StackOverFlow &#127831;</title>
  <link rel="shortcut icon" type="image/x-icon" href="https://image.flaticon.com/icons/png/512/2057/2057586.png" />
</head>

<body>
  <h3>Stack Over Flow &#127831;</h3>

  <input id="yourNumber" type="text" value="837465">

  <button onclick="getTotal()">get the answer</button>
  
  <p id="answer">Answer will be here: </p>

</body>

</html>

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