1557820969

# Working with Numbers in JavaScript

Numbers and mathematics come into most scripts at some point, be it in the form of the simple arithmetic required to add up prices and work out sales tax, the process of generating and using random numbers, or the more complex mathematics involved animation.

In this article we’ll meet the basic constructs for number crunching in JavaScript, and look at some fairly simple, but useful snippets.

### Doing Math in JavaScript

JavaScript provides syntax for basic arithmetic, as well as a range of properties and methods for performing more complex tasks.

There are five arithmetic operators in JavaScript, each of which is represented by a special character: multiplication (*), division (/), addition (+), subtraction (-), and modulus(%).

Math Operators

In addition to these basic operators, JavaScript has a built-in Math object that provides a range of mathematical methods and properties. The most useful methods are:

Math.ceil : rounds a number upwards, so Math.ceil(8.23) returns 9

Math.floor : rounds a number downwards, so* Math.floor(23.8)* returns 23

Math.round : rounds the number to the nearest integer, so *Math.round(8.3) *returns 8, while Math.round(2.8) returns 3

Math.pow : raises one number to the power of another so *Math.pow(2,3)*returns

Math.sqrt : returns the square root of a number do *Math.sqrt(9) *returns 3

Math.random : returns a pseudorandom number between zero and one

### Rounding a Number to x Decimal Places

In some applications, you may need to round the result to a certain number of decimal places. For instance, you may want to display temprature values in 0.1 degree increments, even you though your script has access to more precise values.

So the question is how to do it?

We can write a function that will round to any number of places, as follows:

JavaScript function to round any numbers

So, for example, if we started with a number like n = 3.492867, we could call roundTo(n, 0) to get 3 or roundTo(n, 2) to get 3.49

### Creating and Constraining Random Numbers

Random numbers can be used as the basis for any task that needs to have a random or semi-random aspect.

We already know how to generate a random number between 0 and 1 by using Math.random() function but what if we need random numbers between 0-100 or maybe 8-23 or 23-1995 etc.

Well there is a solution

We can obtain a random integer within specified limits using a combination of the Math object’s random and round methods, which we saw in “Doing Math in JavaScript”.

function to generate random number between any two numbers.

so, for example we could generate a number between 0 and 100 by calling randomBetween(0, 100), or a number between 8 and 1995 by calling radomBetween(8, 1995).

using randomBetween() function to get random numbers.

### Converting a Number to a String

Once you’ve finished a calculation, you might want to turn the output into something more readable, such as formatting a value to represent currency.To do this we must convert the number to a string.

The most direct means of converting a number to a string is to built -in String constructor function:

converting number to string using built-in String constructor

You can also use toString method, which is provided for every number value in JavaScript:

converting string using toString() method

Another useful technique is string concatenation (joining strings together), which returns a string even if some of the input values are numbers:

string concatenation

### Converting a String to a Number

Like Number to String, conversion of String to a Number is also possible.

In general, you can treat a JavaScript string that contains a number as if it were a number, and JavaScript will Perform the string-to-number conversion for you automatically. But sometimes you need to extract a number from a string, or exercise more control over how the conversion is done.

The most direct means of converting a string to a number is to use the built-in Number constructor function:

conversion using built-in Number constructor function

Another handy technique is to use tha parseInt and ParseFloat functions, which will attempt to find and return an integer or decimal number at the start of a string.

conversion using parseInt and parseFloat

**note : **If the first character of the input is not a digit or some other numerical character , these functions will not be ale to return a number. In such cases. they’ll return the special value NaN (Not a Number).

#javascript

1622207074

## What is JavaScript - Stackfindover - Blog

Who invented JavaScript, how it works, as we have given information about Programming language in our previous article ( What is PHP ), but today we will talk about what is JavaScript, why JavaScript is used The Answers to all such questions and much other information about JavaScript, you are going to get here today. Hope this information will work for you.

## Who invented JavaScript?

JavaScript language was invented by Brendan Eich in 1995. JavaScript is inspired by Java Programming Language. The first name of JavaScript was Mocha which was named by Marc Andreessen, Marc Andreessen is the founder of Netscape and in the same year Mocha was renamed LiveScript, and later in December 1995, it was renamed JavaScript which is still in trend.

## What is JavaScript?

JavaScript is a client-side scripting language used with HTML (Hypertext Markup Language). JavaScript is an Interpreted / Oriented language called JS in programming language JavaScript code can be run on any normal web browser. To run the code of JavaScript, we have to enable JavaScript of Web Browser. But some web browsers already have JavaScript enabled.

Today almost all websites are using it as web technology, mind is that there is maximum scope in JavaScript in the coming time, so if you want to become a programmer, then you can be very beneficial to learn JavaScript.

## JavaScript Hello World Program

In JavaScript, ‘document.write‘ is used to represent a string on a browser.

``````<script type="text/javascript">
document.write("Hello World!");
</script>
``````

## How to comment JavaScript code?

• For single line comment in JavaScript we have to use // (double slashes)
• For multiple line comments we have to use / * – – * /
``````<script type="text/javascript">

//single line comment

/* document.write("Hello"); */

</script>
``````

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## The essential JavaScript concepts that you should understand

As a JavaScript developer of any level, you need to understand its foundational concepts and some of the new ideas that help us developing code. In this article, we are going to review 16 basic concepts. So without further ado, let’s get to it.

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## How to Use Zapier with MongoDB

I’m a huge fan of automation when the scenario allows for it. Maybe you need to keep track of guest information when they RSVP to your event, or maybe you need to monitor and react to feeds of data. These are two of many possible scenarios where you probably wouldn’t want to do things manually.

There are quite a few tools that are designed to automate your life. Some of the popular tools include IFTTT, Zapier, and Automate. The idea behind these services is that given a trigger, you can do a series of events.

In this tutorial, we’re going to see how to collect Twitter data with Zapier, store it in MongoDB using a Realm webhook function, and then run aggregations on it using the MongoDB query language (MQL).

## The Requirements

There are a few requirements that must be met prior to starting this tutorial:

• A properly configured MongoDB Atlas cluster

There is a Zapier free tier, but because we plan to use webhooks, which are premium in Zapier, a paid account is necessary. To consume data from Twitter in Zapier, a Twitter account is necessary, even if we plan to consume data that isn’t related to our account. This data will be stored in MongoDB, so a cluster with properly configured IP access and user permissions is required.

You can get started with MongoDB Atlas by launching a free M0 cluster, no credit card required.

While not necessary to create a database and collection prior to use, we’ll be using a zapier database and a tweets collection throughout the scope of this tutorial.

## Understanding the Twitter Data Model Within Zapier

Since the plan is to store tweets from Twitter within MongoDB and then create queries to make sense of it, we should probably get an understanding of the data prior to trying to work with it.

We’ll be using the “Search Mention” functionality within Zapier for Twitter. Essentially, it allows us to provide a Twitter query and trigger an automation when the data is found. More on that soon.

As a result, we’ll end up with the following raw data:

``````{
"created_at": "Tue Feb 02 20:31:58 +0000 2021",
"id": "1356701917603238000",
"id_str": "1356701917603237888",
"full_text": "In case anyone is interested in learning about how to work with streaming data using Node.js, I wrote a tutorial about it on the @MongoDB Developer Hub. https://t.co/Dxt80lD8xj #javascript",
"truncated": false,
"display_text_range": [0, 188],
"iso_language_code": "en",
"result_type": "recent"
},
"user": {
"id": "227546834",
"id_str": "227546834",
"name": "Nic Raboy",
"screen_name": "nraboy",
"location": "Tracy, CA",
"description": "Advocate of modern web and mobile development technologies. I write tutorials and speak at events to make app development easier to understand. I work @MongoDB.",
"url": "https://t.co/mRqzaKrmvm",
"entities": {
"url": {
"urls": [
{
"url": "https://t.co/mRqzaKrmvm",
"expanded_url": "https://www.thepolyglotdeveloper.com",
"display_url": "thepolyglotdeveloper.com",
"indices": [0, 23]
}
]
},
"description": {
"urls": ""
}
},
"protected": false,
"followers_count": 4599,
"friends_count": 551,
"listed_count": 265,
"created_at": "Fri Dec 17 03:33:03 +0000 2010",
"favourites_count": 4550,
"verified": false
},
"lang": "en",
"text": "In case anyone is interested in learning about how to work with streaming data using Node.js, I wrote a tutorial about it on the @MongoDB Developer Hub. https://t.co/Dxt80lD8xj #javascript"
}
``````

The data we have access to is probably more than we need. However, it really depends on what you’re interested in. For this example, we’ll be storing the following within MongoDB:

``````{
"created_at": "Tue Feb 02 20:31:58 +0000 2021",
"user": {
"screen_name": "nraboy",
"location": "Tracy, CA",
"followers_count": 4599,
"friends_count": 551
},
"text": "In case anyone is interested in learning about how to work with streaming data using Node.js, I wrote a tutorial about it on the @MongoDB Developer Hub. https://t.co/Dxt80lD8xj #javascript"
}
``````

Without getting too far ahead of ourselves, our analysis will be based off the `followers_count` and the `location` of the user. We want to be able to make sense of where our users are and give priority to users that meet a certain followers threshold.

## Developing a Webhook Function for Storing Tweet Information with MongoDB Realm and JavaScript

Before we start connecting Zapier and MongoDB, we need to develop the middleware that will be responsible for receiving tweet data from Zapier.

Remember, you’ll need to have a properly configured MongoDB Atlas cluster.

We need to create a Realm application. Within the MongoDB Atlas dashboard, click the Realm tab.

For simplicity, we’re going to want to create a new application. Click the Create a New App button and proceed to fill in the information about your application.

From the Realm Dashboard, click the 3rd Party Services tab.

We’re going to want to create an HTTP service. The name doesn’t matter, but it might make sense to name it Twitter based on what we’re planning to do.

Because we plan to work with tweet data, it makes sense to call our webhook function tweet, but the name doesn’t truly matter.

With the exception of the HTTP Method, the defaults are fine for this webhook. We want the method to be POST because we plan to create data with this particular webhook function. Make note of the Webhook URL because it will be used when we connect Zapier.

The next step is to open the Function Editor so we can add some logic behind this function. Add the following JavaScript code:

``````exports = function (payload, response) {

const collection = context.services.get("mongodb-atlas").db("zapier").collection("tweets");

return collection.insertOne(tweet);

};
``````

In the above code, we are taking the request payload, getting a handle to the tweets collection within the zapier database, and then doing an insert operation to store the data in the payload.

There are a few things to note in the above code:

1. We are not validating the data being sent in the request payload. In a realistic scenario, you’d probably want some kind of validation logic in place to be sure about what you’re storing.
2. We are not authenticating the user sending the data. In this example, we’re trusting that only Zapier knows about our URL.
3. We aren’t doing any error handling.

When we call our function, a new document should be created within MongoDB.

By default, the function will not deploy when saving. After saving, make sure to review and deploy the changes through the notification at the top of the browser window.

## Creating a “Zap” in Zapier to Connect Twitter to MongoDB

So, we know the data we’ll be working with and we have a MongoDB Realm webhook function that is ready for receiving data. Now, we need to bring everything together with Zapier.

For clarity, new Twitter matches will be our trigger in Zapier, and the webhook function will be our event.

Within Zapier, choose to create a new “Zap,” which is an automation. The trigger needs to be a Search Mention in Twitter, which means that when a new Tweet is detected using a search query, our events happen.

For this example, we’re going to use the following Twitter search query:

``````url:developer.mongodb.com -filter:retweets filter:safe lang:en -from:mongodb -from:realm
``````

The above query says that we are looking for tweets that include a URL to developer.mongodb.com. The URL doesn’t need to match exactly as long as the domain matches. The query also says that we aren’t interested in retweets. We only want original tweets, they have to be in English, and they have to be detected as safe for work.

In addition to the mentioned search criteria, we are also excluding tweets that originate from one of the MongoDB accounts.

In theory, the above search query could be used to see what people are saying about the MongoDB Developer Hub.

With the trigger in place, we need to identify the next stage of the automation pipeline. The next stage is taking the data from the trigger and sending it to our Realm webhook function.

As the event, make sure to choose Webhooks by Zapier and specify a POST request. From here, you’ll be prompted to enter your Realm webhook URL and the method, which should be POST. Realm is expecting the payload to be JSON, so it is important to select JSON within Zapier.

We have the option to choose which data from the previous automation stage to pass to our webhook. Select the fields you’re interested in and save your automation.

The data I chose to send looks like this:

``````{
"created_at": "Tue Feb 02 20:31:58 +0000 2021",
"location": "Tracy, CA",
"follower_count": "4599",
"following_count": "551",
"message": "In case anyone is interested in learning about how to work with streaming data using Node.js, I wrote a tutorial about it on the @MongoDB Developer Hub. https://t.co/Dxt80lD8xj #javascript"
}
``````

The fields do not match the original fields brought in by Twitter. It is because I chose to map them to what made sense for me.

When deploying the Zap, anytime a tweet is found that matches our query, it will be saved into our MongoDB cluster.

## Analyzing the Twitter Data in MongoDB with an Aggregation Pipeline

With tweet data populating in MongoDB, it’s time to start querying it to make sense of it. In this fictional example, we want to know what people are saying about our Developer Hub and how popular these individuals are.

To do this, we’re going to want to make use of an aggregation pipeline within MongoDB.

Take the following, for example:

``````[
{
"follower_count": {
"\$toInt": "\$follower_count"
},
"following_count": {
"\$toInt": "\$following_count"
}
}
}, {
"\$match": {
"follower_count": {
"\$gt": 1000
}
}
}, {
"\$group": {
"_id": {
"location": "\$location"
},
"location": {
"\$sum": 1
}
}
}
]
``````

There are three stages in the above aggregation pipeline.

We want to understand the follower data for the individual who made the tweet, but that data comes into MongoDB as a string rather than an integer. The first stage of the pipeline takes the `follower_count` and `following_count` fields and converts them from string to integer. In reality, we are using `\$addFields` to create new fields, but because they have the same name as existing fields, the existing fields are replaced.

The next stage is where we want to identify people with more than 1,000 followers as a person of interest. While people with fewer followers might be saying great things, in this example, we don’t care.

After we’ve filtered out people by their follower count, we do a group based on their location. It might be valuable for us to know where in the world people are talking about MongoDB. We might want to know where our target audience exists.

The aggregation pipeline we chose to use can be executed with any of the MongoDB drivers, through the MongoDB Atlas dashboard, or through the CLI.

## Conclusion

You just saw how to use Zapier with MongoDB to automate certain tasks and store the results as documents within the NoSQL database. In this example, we chose to store Twitter data that matched certain criteria, later to be analyzed with an aggregation pipeline. The automations and analysis options that you can do are quite limitless.

If you enjoyed this tutorial and want to get engaged with more content and like-minded developers, check out the MongoDB Community.

This content first appeared on MongoDB.

Original article source at: https://www.thepolyglotdeveloper.com/