Using Variables In Node Js Quick And Brief 2023
Table of Contents
Using variables in node.js – how to use variables of different types
Explaining Scope of a variable
Derive the importance of defining a variable.
Determining the input type of a variable.
In any programming language, variables are an essential part of the code. They allow you to store and manipulate data, which is at the heart of any application. This comprehensive step-by-step tutorial will walk you through the process of setting up and using variables in Node.js.
What Are Variables in a programming language?
A variable is a container to store some data which can be accessed or altered later. It is defined by a type, name, and a value. The value can be a string, date, number, an information in the memory, reference to a code block or a result of a calculation.
Like every programming language a variable is used for the same fixed purpose as defined above and the same principles and use cases applies for using variables in node.js.
How to declare the type and name of a variable in node.js?
The most common way to is to use a keyword mentioning the type of variable followed by the name of the variable and then assigning a value to it.
var stringData = "welcome to node.js coding"
var numberData = 123
var decimalData = 123.4567
This is how basically a variable is defined and declared in node.js, later in this article we will see how to change or alter the contents of a variable.
What are the most commonly used types of variables in programming?
The most common types of variables every programming languages have are :
String – characters or pieces of text
Number – numbers that represent a specific quantity
Boolean – true or false evaluation based on a condition
Arrays – stores arrays which can be single or multi-dimensional values of the above defined variable types
These are the most widely used variable types in node.js and the use case for each type of variables has its own set of properties and goals attached to them which we will describe here.
What are the characteristics of a variable in a programming language?
Type – specifies what kind of values to hold(either one of Integer, float, string etc)
Name – describes the name of the variable through which it can be accessed
Scope – specifies the accessible span of the variable(Global or local)
Here is the description of these characteristics
Using variables in node.js – how to use variables of different types
Number data type variables are used to store numeric data, such as numbers, percentages, and decimals. They can either be integer or floating point, and they can take on any value between -9007199254740991 and 9007199254740991 to store in such variables. The floating point variables have a larger decimal point storage capability.
String variables are used to store text data, such as names, addresses, and phone numbers. They can also contain special characters, and they can be either single or double-quoted.
var customer1Email = "[email protected]" //used to store email address
var customer1Name = "John Doe" // to store the name of the customer
Boolean variables are used to store two states in order to conclude the result of an evaluation which can be true or false.
For Example –
var booleanVal = false //initially we set the value to be false, and we will use this to evaluate an expression
var a = 5, b =7
if(a < b) //expression to find if value of a is less than b
booleanVal = true
else
booleanVal = false
console.log(booleanVal); //this will print true in the console as value of a = 5 is less than b = 7
Object variables are used to store objects, such as arrays, lists, and dictionaries. They can contain any type of data, and they can also have properties and methods.
var stringData = "welcome to node.js coding" (This defines a string data type which can store some alphabetical letters or a sentence, here we have defined the variable type "var" which means a value inside this can be changed later in the execution. Then the name of the variable is stringData followed by assignment operator which works to assign the sentence "welcome to node.js coding" inside the variable, and then to store that sentence in it)
var numberData = 123 (here we have assigned integer value of 123 and store it in the variable numberData)
var decimalData = 123.4567 (here we have assigned float variable value of 123.4567 and store it in the variable decimalData)
var stringDataCopy = stringData
Here we access the value "welcome to node.js coding" which the stringData had stored inside it, and assign the value to another variable stringDataCopy.
To hold a value as a result of a calculation –
var calcResult = 2 * 4. (Resulting value of 8)
The variable calcResult will hold the calculated value of multiplying 2 and 4 which will be 8.
Once you have created a variable, you can access its value at any time by using the variable’s name. This makes it easy to manipulate data without having to remember the exact contents of the data set.
We can manipulate the value of this
calcResult = calcResult * 2 (note that we have defined the variable calcResult previously by mentioning the "var" keyword. So now we can access the variable with its name and then perform desired operations) Know more about keywords in node.js
Here we have multiplied the value of 8 with 2 and assigned the result on the calcResult variable itself. Thus the value it was holding was manipulated. We can further manipulate or simply reassign the value as much we want.
We can reassign the value by –
calcResult = 30
Thus now the value is again manipulated and now it holds a value of 30 in place of 16 which was stored in it previously.
Arrays – Arrays are used to store a series of data in a predictable order, to store data in a linear format or are used in calculating and comparing data that are ordered.
For example –
var numericArray = [1,2,3,4,5,6] //single dimensional array to store numeric data from 1 to 6
To access the whole array we will use the name of the variable as usual
To access a specific part we will use the name of the variable along with the index or position of the element we want to access.
So to access the number 5 we will write numericArray[4], here we have written 4 because index of the array will start with 0, more specifically like this
Values 1,2,3,4,5,6
Index 0,1,2,3,4,5
So to access the first number 1 we write numericArray[4], for the last one we write numericArray[5], and so on.
What are the different types of scopes of a variable in programming?
A variable’s scope defines the area of code in which it can be used. A global scope, can be used in all the code that is executed. A local/block/fixed scope can be used only in the code that is executed within the same function or block.
Explaining Scope of a variable
Consider the following piece of code with global scope and local scope –
var someData = "this code is defined in a global variable"
// this is a global scope
function displayData() //this starts a local scope with a opening curly braces
// this is a local scope
var input = someData
console.log(input) // Since someData was defined outside this function, the scope of this function starts and ends with the curl braces, since someData has a global scope meaning prints out "this code is defined in a global variable".
// if someData was defined inside this function which is a local scope then this value can only be accessed inside this function only and after the closing curly braces the variable someData won’t be recognised, like if we want to access it in the function changeValue or any other function someData won’t be recognised.
var dataWithLocalScope = " this is a value inside a local scope which cannot be accessed in other parts of the program"
//this closes the local scope with a closing curly braces
function changeValue() //this starts a local scope with a opening curly braces
// this is a local scope, so the variable which was defined inside the function displayData, which was dataWithLocalScope cannot be accessed here since that variable’s access is only limited to the function displayData, but the variable someData was defined in a global scope, means outside this function so it can be accessed here as well as any part to the program.
var changedVal = someData
changedVal = "This variable is now being changed"
console.log(change) // prints out "This variable is now being changed", here we have just accessed the global variable with its name "someData" and assigned it to a new variable named change and then reassigned/altered its value to a new sentence "This variable is now being changed"
//since changedVal variable is inside the local scope we have access to it inside this function only
//this closes the local scope with a closing curly braces
�� key Takeaway: Variables have a global, local/fixed/block scope, depending on the circumstances and desired outcomes. A variable’s scope is important because it determines which areas of the program the variable will be recognised by the compiler.
Derive the importance of defining a variable.
When we write code, we need to be able to define variables. A variable is a name for a piece of information that we can use to store data. Variables are important because they allow us to easily reference that data later on.
Variables can be defined in a number of programming languages, but they all have a few common features. At first variables must be assigned a value and declare the type but since javascript/nodejs has automatic type detection which is dynamic in nature, the complier is able to detect the type of variable automatically and determines that whether the variable is a string, number, array, boolean, date or null. After that, variables can be referenced in our code by calling its name. This means that we can use the name of the variable to access the data it contains.
There are a few other things that variables can do. For example, variables can be used to hold temporary data. This allows you to avoid having to create and manage multiple variables for the same purpose. Also, variables can be used to store data in different places in your code. This allows you to more easily keep track of where the data is stored.
�� key Takeaway: Defining variables is an important part of programming. They allow you to easily reference data later on and store data in different places in your code. Additionally, variables can be used to hold temporary data, avoid having to create and manage multiple variables, and store data in different languages.
What are the uses and benefits of a variable in programming?
There are a number of different uses for variables in programming. Here are five examples:
– store the value of the corresponding type it was declared
– store the result of a calculation or an expression.
– store the name of a object or function.
– store the location of a file or directory.
– store the value of a parameter passed to a function.
While using variables in node.js, variables are used to keep track of the information it has stored while the program is running. This information can be used later to further perform calculations, store data, reassign new data or perform other tasks. Variables can be assigned a specific value at the start of the program, or they can be left undefined.
The most specific use case of a variable with undefined value is to make it have a global scope then we can assign, change, manipulate or reassign values from the beginning of the program till the end.
For example we can use it in several functions so as to access the results of the previous functions inside further functions which will make them interdependent on each other. So as it has a global scope it can be accessed from any part of the program.
Variables can have a variety of uses outside their original scope. For example, you can use variables to store data for a game or to track the progress of a calculation. You can also use variables to store information about the user (for example, the user’s name or email address).
Further variables can be used in many different ways. Here are some examples:
– To store a map in a map format
– To store an object in an object format
Finally, you can use the variable in your code. You can access the variable by using its name or by using the variable’s value.
�� key Takeaway: Variables allow you to store data in a specific location so that you can access it later. Variables can be used in many different ways, and you need to specify their type, location, and use.
Determining the input type of a variable.
When you define a variable in node.js, you have to determine the input type. There are six different input types of variables:
– Boolean: Stores either true or false.
– String: Stores a sequence of characters.
– Number: Stores any number.
– Null: Stores nothing, typically this is a result of a particular operation which is most of the times thrown by the compiler
– Reference: Refers to a particular object.
-Date and time: This will store the date and time
�� key Takeaway: When you define a variable, you determine the input type. There are six different types of variables, each with its own specific use.
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