How to generate a random number from an array using Javascript?

Question

I am trying to generate a random SKU number from the array. Using Math.floor() and Math.random() to get the index. But it only returns a letter or number instead of the entire string. Here is the function:

function bookRentData(bookData) {

   bookData.forEach((book) => {

      //generate random sku number

      const sku = book.sku
      var random = sku[Math.floor(Math.random() * sku.length - 1)];
      document.getElementById("message").innerHTML = sku[random];   

      });
        wrap.innerHTML += `<tr>
                             <td>${book.sku}</td>
                             <td>${book.price}</td>
                          </tr>`
   }

expected output: 101ZS536

current output: Z

// example of the data 

         [{sku: '101ZS536',
            price: 4.37
          },
          {
            sku: '10134QYT',
            price: 42.61
          },
          {
            sku: '10134QYT',
            price: 53.31
          },
          {
            sku: '10134QYT',
            price: 0
          },
          {
            sku: '10134QYT',
            price: 3.46
          }
        ]

Any advice or suggestions will be highly appreciated.

What is bookData? Why do you use .forEach()? What is book.sku/sku? If you answer all those questions you should find the source of your problem. — Andreas
– Andreas, Commented Jun 19, 2020 at 17:31
Its returning z because sku value is set equal to [1,0,1,Z,S,5,3,6]. i.e. the value of book.sku — Random COSMOS
– Random COSMOS, Commented Jun 19, 2020 at 17:36
@Andreas bookData holds the entire data, .forEach() goes over each object in the data and book.sku returns each book sku number from each object. I am trying to retrieve 1 of those sku numbers randomly. — Sam
– Sam, Commented Jun 19, 2020 at 19:36

Tony Tom · Accepted Answer · 2020-06-20 05:58:43Z

1

Check this satisfies your scenario.

function bookRentData() {
var bookData =  [{sku: '101ZS536',
            price: 4.37
          },
          {
            sku: '10134QYT',
            price: 42.61
          },
          {
            sku: '10134QXT',
            price: 53.31
          },
          {
            sku: '10134QZT',
            price: 0
          },
          {
            sku: '10134QST',
            price: 3.43
          },
           {
            sku: '10134QCT',
            price: 3.46
          },
           {
            sku: '10134QYT',
            price: 3.1
          },
           {
            sku: '10134QYT',
            price: 3.2
          },
           {
            sku: '10134QBT',
            price: 3.6
          },
           {
            sku: '10134QYT',
            price: 3.5
          },
          {
            sku: '10134QJT',
            price: 3.1
          },
           {
            sku: '10134QYT',
            price: 3.2
          },
           {
            sku: '10134QRT',
            price: 3.6
          },
           {
            sku: '10134QKT',
            price: 3.5
          }
          
        ];
   book = bookData[Math.floor(Math.random() * bookData.length)]
   var x = document.getElementById("demo")
   x.innerHTML = book.sku;
       
}

<!DOCTYPE html>
<html>
<body>

<p>Test</p>

<button onclick="bookRentData()">Try it</button>

<p id="demo"></p>

edited Jun 20, 2020 at 5:58

answered Jun 19, 2020 at 17:49

Tony Tom

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2 Comments

Sam Over a year ago

Thanks, but this returns an entire object. I am only trying to retrieve the SKU number from the array of objects. In this case, 10134QYT. Later, I will update the price.

Tony Tom Over a year ago

You can take the SKU number from the object, right? Check the updated snippet

Aaron Plocharczyk · Accepted Answer · 2020-06-20 01:18:26Z

0

Here's a simple and readable answer that uses rando.js to access a random value from the array and then accesses the sku of that object:

var arr = [
  {sku: '123ZS536', price: 4.37},
  {sku: '45634ABC', price: 42.61},
  {sku: '10134DEF', price: 53.31},
  {sku: '78934GHI', price: 0},
  {sku: '10134QYT', price: 3.46}
];

console.log( rando(arr).value.sku );

<script src="https://randojs.com/1.0.0.js"></script>

If you want to use this code, don't forget to put that script tag in the head of your html document.

answered Jun 20, 2020 at 1:18

Aaron Plocharczyk

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Comments

Random COSMOS · Accepted Answer · 2020-06-19 17:41:03Z

0

Maybe this will work:

function bookRentData(bookData) {
   book = bookData[Math.floor(Math.random() * bookData.length - 1)]

        wrap.innerHTML += `<tr>
                             <td>${book.sku}</td>
                             <td>${book.price}</td>
                          </tr>`
}

I assume you want a single sku from the list as you need a random one. (And if you want all then no need for them to be random.)

PS comment if I didn't understand your question correctly

answered Jun 19, 2020 at 17:41

Random COSMOS

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2 Comments

Sam Over a year ago

this returns the entire object. I am just trying to get the SKU number. Thanks!

Random COSMOS Over a year ago

Yup book is an object but your inner html will have the no. only as it's book.sku

Rahul Bhobe · Accepted Answer · 2020-06-19 18:49:18Z

0

You have Math.floor(Math.random() * sku.length - 1), which might sometimes return -1.

To generate a number between 0 to length, you can change to:

      var random = sku[Math.floor(Math.random() * sku.length)];

edited Jun 19, 2020 at 18:49

answered Jun 19, 2020 at 17:47

Rahul Bhobe

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