Add values of javascript array

Question

I'm trying to complete a system with which a book shop can enter the a sample of 5 books that were sold that day along with their prices. These values would then be displayed to the page. I have managed this and now wish to add the total price. I have tried all the methods mentioned on stack overflow and elsewhere to get the sume of the price array but I either get the last price entered or "NaN" when i try to get the total. Please help!!! Here is my code

document.addEventListener("DOMContentLoaded", function() {
  enterBooks()
}); // Event listener - When page loads, call enterBooks function

function enterBooks() { // enterBooks function
  
  var books = []; // Defines books variable as an array
  
  for (var i = 0; i < 5; i++) { // for loop to loop 5 times
    
    books.push("<li>" + prompt("Enter a book") + "</li>"); // PUSH adds a new item to the array in the form of a prompt with <li> tags either side of each.

    var price = []; // Defines price variable as an array
    
    for (var p = 0; p < 1; p++) { // for loop to loop 1 time
      
      price.push("<li>" + "£" + parseInt(prompt("Enter the price")) + "</li>"); // Once again PUSH adds a new item to the array in the form of a prompt with <li> tags either side of each. This then displays next to each book.

    }
    document.getElementById("displayPrice").innerHTML += (price.join(""));
    document.getElementById("displayBooks").innerHTML = (books.join(""));
  }
  // --------- This is the part i cannot seem to get -----------
  var total = 0;

  for (var t = 0; t < price.length; t++) {
    total = total + price[t];
  }
  document.getElementById("total").innerHTML = total;
}

ul {
    list-style-type: decimal; /* Gives list items numbers */
    font-size:25px;
    width:20%;
}
#displayBooks {
    float:left;
    width:20%;
}
#displayPrice {
    float:left;
    width:50%;
    list-style-type: none;
}

<!DOCTYPE html>
<html>

<head>
  <title>Bookshop</title>
  <link href="css/style.css" rel="stylesheet">
  <!-- StyleSheet -->
</head>


<body class="text-center">
  <h1>BookShop</h1> 
  <!-- Header -->
  <h3>Books sold</h3> 
  <!-- Team intro -->
  <ul id="displayBooks">
    <!-- Div to display the teams -->

  </ul>
  <ul id="displayPrice">
    <!-- Div to display the teams -->

  </ul>
  <div id="total">

  </div>

  <script src="js/script.js"></script>
</body>

</html>

P.S This is my first time asking a question on here so if it's not structured very well then I apologise in advance and hope you can still make it all out

price is an array of strings of HTML; you can't add them up. — user663031, Commented Feb 29, 2016 at 14:05

Alexandr Kudryashov · Accepted Answer · 2016-02-29 14:13:08Z

try this:

document.addEventListener("DOMContentLoaded", function() {
  enterBooks()
}); // Event listener - When page loads, call enterBooks function

function enterBooks() { // enterBooks function
  
  var books = []; // Defines books variable as an array
  var price = [];
  var priceText=[];
  for (var i = 0; i < 5; i++) { // for loop to loop 5 times
    
    books.push("<li>" + prompt("Enter a book") + "</li>"); // PUSH adds a new item to the array in the form of a prompt with <li> tags either side of each.
      price[i]=parseInt(prompt("Enter the price"));
      priceText.push("<li>" + "£" + price[i] + "</li>"); // Once again PUSH adds a new item to the array in the form of a prompt with <li> tags either side of each. This then displays next to each book.

 
    document.getElementById("displayPrice").innerHTML = priceText.join("");
    document.getElementById("displayBooks").innerHTML = (books.join(""));
  }
  // --------- This is the part i cannot seem to get -----------
  var total = 0;

  for (var t = 0; t < price.length; t++) {
    total = total + price[t];
  }
  document.getElementById("total").innerHTML = total+ "£";
}

ul {
    list-style-type: decimal; /* Gives list items numbers */
    font-size:25px;
    width:20%;
}
#displayBooks {
    float:left;
    width:20%;
}
#displayPrice {
    float:left;
    width:50%;
    list-style-type: none;
}

<!DOCTYPE html>
<html>

<head>
  <title>Bookshop</title>
  <link href="css/style.css" rel="stylesheet">
  <!-- StyleSheet -->
</head>


<body class="text-center">
  <h1>BookShop</h1> 
  <!-- Header -->
  <h3>Books sold</h3> 
  <!-- Team intro -->
  <ul id="displayBooks">
    <!-- Div to display the teams -->

  </ul>
  <ul id="displayPrice">
    <!-- Div to display the teams -->

  </ul>
  <div id="total">

  </div>

  <script src="js/script.js"></script>
</body>

</html>

Also, I would vote you up but I can't because Stack overflow knows i'm a noob! — Eli Nathan, Commented Feb 29, 2016 at 14:53

Jagrut · Accepted Answer · 2016-02-29 14:06:56Z

0

It is because you are adding the entire HTML in the price array and hence it will not add as it is not numerical data.

This should work:

var input = parseInt(prompt("Enter the price"));
price.push(input);

answered Feb 29, 2016 at 14:06

Jagrut

9227 silver badges21 bronze badges

Add a comment |

Nina Scholz · Accepted Answer · 2016-02-29 14:09:24Z

please change

for (var p = 0; p < 1; p++) { // for loop to loop 1 time
    price.push("<li>" + "£" + parseInt(prompt("Enter the price")) + "</li>"); // Once again PUSH adds a new item to the array in the form of a prompt with <li> tags either side of each. This then displays next to each book.
}
document.getElementById("displayPrice").innerHTML += (price.join(""));

to

// no need for loop
price.push(parseInt(prompt("Enter the price"), 10)); // just the price, added base to parseInt (really? not parseFloat?)
document.getElementById("displayPrice").innerHTML += price.map(function (a) {
    return '<li>GBP' + a + '</li>'; // build here the string for output
}).join("");

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