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NodeJs DataType

Primitive Datatypes of Node.js

number

boolean

string

object

Non-primitive datatype of nodejs

There are two non-primitive datatypes of node.js

array

function

undefined

The value undefined means that a value has not been set yet or simply does not exist.

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var x;
console.log(x);
output : undefined

var y;
console.log(y);

y = null ;
console.log(y);
output : undefined
null

typeof

To see the type of anything in JavaScript, use the typeof operator:

console.log(typeof 5);
console.log(typeof "sana");
console.log(typeof function () { var x = 10; });

output :- number
string
function

Type Comparisons and Conversions

JavaScript has both the equality operator == and the precise equality operator ===.

console.log(101 == '101');
console.log(786 === '786');
console.log(84 == 'sana');
console.log("sana" == "SANA");
console.log("sana".toUpperCase() == "SANA");
output :-
true
false
false
false
true

To check arguments to functions:

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function fine(param) {
if (param == null || param == undefined || param == '')
throw new Error("Invalid Argument");
}
function better(param) {
if (!param)
throw new Error("Invalid Argument");
}

Number :-

The number data type in Node.js is 64 bits floating point number both positive and negative. The parseInt() and parseFloat() functions are used to convert to number, if it fails to convert into a number then it returns NaN.

File Name :

var x = 5;
var y = 10;
var z = 07;
console.log(x);
console.log(y);
console.log(z);

var n1 = 1;
var n2 = 2;
console.log(n1 + 1);
console.log(n1 / n2);
console.log(n1 * n2);
console.log(n1 - n2);
console.log(n1 % 2);

parseInt OR parseFloat function

You can use the functions parseInt and parseFloat to convert strings to numbers.

console.log(parseInt("10"));
console.log(parseFloat("8.4"));
console.log(parseInt("84.123"));
console.log(parseFloat("20"));

Note :-

If we use these functions with not-parsable value such as string, they return the special value NaN:

console.log(parseInt("sana"));
console.log(parseFloat("mahi"));
Output :- NaN

To test the NaN you use the isNaN();
isNaN(parseInt("sana"));

Boolean :-

Boolean data type is a data type that has one of two possible values, either true or false. The boolean() function is used to convert any data type to a boolean value. According to the rules, false, 0, NaN, null, undefined, empty string evaluate to false and other values evaluates to true.

console.log(0 == false);
console.log("" == false);
if(null){
}else{
console.log("false");
}
if(undefined){
}else{
console.log("false");
}
if(NaN){
}else{
console.log("false");
}
output :-
true
true
false
false
false

example Boolean

var myData = true;
console.log(myData); // true
// Boolean operations (&&, ||, !) work as expected:
console.log(true && true); // true
console.log(true && false); // false
console.log(true || false); // true
console.log(false || false); // false
console.log(!true); // false
console.log(!false); // true

string

Strings in Node.js are sequences of unicode characters. Strings can be wrapped in a single or double quotation marks. Javascript provide many functions to operate on string, like indexOf(), split(), substr(), length.

var x = "Welcome to ittutorial";
console.log(x);

console.log('Sana\'s tutorial.')
console.log("\"Hey, Sana!\", how are you.")
Output of the above code:
Welcome to ittutorial
Sana's tutorial.
"Hey, Sana!", how are you.

Node.js Object

Object is an extremely dynamic and flexible data type. Object notation is super readable and compact. Objects are written with curly braces {}. In Node.js, an object is a mapping between the keys and values. The keys are strings and the values can be anything. The object properties are written as name:value pairs, separated by commas.

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var users = {
name: "Sana",
age: "03",
address: "Patna"
};
console.log(employee.name);
console.log(employee.age);
console.log(employee.address);

Node.js Array

An array is a collection of key/value pairs. We can store more than one item in only one variable, i.e., Array. So the array is used when there is a requirement to add more items in a single variable. We can create an array in node.js in two different ways, either using the traditional notation or array literal syntax.

var arr1 = new Array();
var arr2 = [];

Example

var arr1 = ['sana', 'mahira', 'mahtab', 'NB'];

for (var i = 0; i < arr1.length; i++) {
console.log(arr1[i]);
}

Node.js Function

A Node.js function is defined with the function keyword, followed by a name. Function parameters are listed inside the parentheses () in the function definition. When the defined function was invoked from a statement, Node.js will return the output of the executed code after the invoking statement.

function msg(name) {
console.log("Hello "+name);
}

msg("sana mahtab");

anonymous function

var x1 = function() {
console.log('Hello');
return true;
}

Output :-

Itechtuto

NodeJs Tutorials

NodeJs DataType

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