How to populate an array with random numbers in JavaScript

by Janeth Kent Date: 07-05-2021 javascript


Some of you might think that what we explained in the article on how to populate an array with numbers, apart from the didactic part, would not have much applicability since we load an array with the same number. It is true that the use cases are fewer, but in order to get the most out of it we are going to see how we can populate an array with random numbers in JavaScript. This way each of the elements of the array we create by default will be different.

In this case, instead of the .fill() method, we are going to use the .from() method. So let's see what is the syntax of the .from() method

 
Array.from(arrayLike[, mapFn[, thisArg]])
 

In this case the first parameter arrayLike has to be an iterable element that we will convert into an array. The second parameter is mapFn which will be a map function that will be executed for each element in the array. This second parameter will play a major role in filling the array elements. And thisArg is the value to use as this in the map function.

Now that we know how the .from() method works, let's see how to fill it in.

The first thing is to give it an iterable element that has ten elements. So we can create an array with the 10 empty elements.

 
new Array(10)
 

But we are going to do it in a different way and write it in a shorthand way with an array instantiation as follows:

 
{length: 10}
 

Now we will focus on the map function. This function is the one that will return the value to assign to each of the array positions. That is why it is here where we return the random number.

 
function() {       
return Math.floor(Math.random() * 10);  
}

 

For the random number we have used the method .random() of the Math object.

This function can be abbreviated with the arrow operator as follows:

 
() => Math.floor(Math.random() * 10)
 

So, if we compose our .from() method, it will look like this:

 
let myarray = Array.from({length: 10}, () => Math.floor(Math.random() * 10));
 

All that remains is to display the array populated with the random numbers.

 
let myarray = Array.from({length: 10}, () => Math.floor(Math.random() * 10));    
myarray.forEach(function(item,index,arr){      
console.log(item);  
});


 

So we have seen that with a single function and a bit of skill we have managed to fill an array with random numbers in JavaScript.

 
by Janeth Kent Date: 07-05-2021 javascript hits : 5215  
 
Janeth Kent

Janeth Kent

Licenciada en Bellas Artes y programadora por pasión. Cuando tengo un rato retoco fotos, edito vídeos y diseño cosas. El resto del tiempo escribo en MA-NO WEB DESIGN END DEVELOPMENT.

 
 
 

Related Posts

Dates in local format with Javascript

In the articles we have about dates in JavaScript we were missing one about how to create dates in local format with JavaScript. That is to say, being able to…

Formatting hours in Javascript

Continuing with the set of articles that talk about internationalisation elements, like the previous one where we talked about relative dates in JavaScript, we will see in this one how…

Request data with prompt in JavaScript

After having published several articles about how to manipulate arrays and dates, today I will publish a post that some of you will find too basic and others will find…

Relative dates in JavaScript

One of the interesting things about the internationalisation library represented in the Int object is the handling of relative dates in Javascript. This handling allows us to represent a date…

How to access webcam and grab an image using HTML5 and Javascript

We often use webcams to broadcast video in real time via our computer. This broadcast can be viewed, saved and even shared via the Internet. As a rule, we need…

The JavaScript forEach loop

We have already talked about how to handle some of loops  types in Javascript including for, for-in and for-off loops. In the case of today we are going to see how…

What are React Hooks and what problems they solve

Working with React, - and before the release of Hooks in version 16.8 -  there was always the possibility to create components in three different ways based on a number of…

Flattening arrays in JavaScript

When we are handling arrays that are arrays or have multiple dimensions it can be very useful to know how to flatten arrays in JavaScript. That is to say, to…

How to populate an array with numbers in JavaScript

Populate an array with numbers in JavaScript The first step is to initialise the array. So today we are going to see a simple way to do it and see how…

Top Javascript Libraries and Frameworks Part 2

What are JavaScript frameworks?   JavaScript frameworks are application frameworks that allow developers to manipulate code to meet their particular needs. Web application development is like building a house. You have the option…

How to Send Email from an HTML Contact Form

In today’s article we will write about how to make a working form that upon hitting that submit button will be functional and send the email (to you as a…

Top JavaScript libraries and frameworks part 1

JavaScript libraries and frameworks make it easy to develop websites and applications with a wide variety of features and functionality, all with dynamic, flexible and engaging features. According to a 2020…

We use our own and third-party cookies to improve our services, compile statistical information and analyze your browsing habits. This allows us to personalize the content we offer and to show you advertisements related to your preferences. By clicking "Accept all" you agree to the storage of cookies on your device to improve website navigation, analyse traffic and assist our marketing activities. You can also select "System Cookies Only" to accept only the cookies required for the website to function, or you can select the cookies you wish to activate by clicking on "settings".

Accept All Only sistem cookies Configuration