JavaScript Syntax

JavaScript syntax refers to the rules and conventions dictating how code is structured and arranged within the JavaScript programming language. This includes statements, expressions, variables, functions, operators, and control flow constructs.

Syntax

console.log("Basic Print method in JavaScript");

JavaScript syntax refers to the set of rules that determines how JavaScript programs are constructed:

// Variable declaration
let c, d, e;

// Assign value to the variable
c = 5; 

// Computer value of variables
d = c;
e = c / d;

JavaScript Values

There are two types of values defined in JavaScript Syntax:

• Fixed Values: These are known as the literals.
• Variable values: These are called variables

These are the features of JavaScript which have some predefined syntax:

JavaScript Literals

Syntax Rules for the JavaScript fixed values are:

• JavaScript Numbers can be written with or without decimals.
• Javascript Strings are text that can be written in single or double quotes.

let num1 = 50
let num2 = 50.05

let str1 = "Geek"
let str2 = 'Geeks'

console.log(num1)
console.log(num2)
console.log(str1)
console.log(str2)

50
50.05
Geek
Geeks

JavaScript Variables

A JavaScript variable is the simple name of the storage location where data is stored. There are two types of variables in JavaScript which are listed below: 

• Local variables: Declare a variable inside of a block or function.
• Global variables: Declare a variable outside function or with a window object.

Example: This example shows the use of JavaScript variables.

// Declare a variable and initialize it
// Global variable declaration
let Name = "Apple";

// Function definition
function MyFunction() {

    // Local variable declaration
    let num = 45;

    // Display the value of Global variable
    console.log(Name);

    // Display the value of local variable
    console.log(num);
}

// Function call
MyFunction();

Output: 

Apple
45

JavaScript Operators

JavaScript operators are symbols that are used to compute the value or in other words, we can perform operations on operands. Arithmetic operators ( +, -, *, / ) are used to compute the value, and Assignment operators ( =, +=, %= ) are used to assign the values to variables.

Example: This example shows the use of javascript operators.

// Variable Declarations
let x, y, sum;

// Assign value to the variables
x = 3;
y = 23;

// Use arithmetic operator to
// add two numbers
sum = x + y;

console.log(sum);

26

JavaScript Expressions

Javascript Expression is the combination of values, operators, and variables. It is used to compute the values.

Example: This example shows a JavaScript expression.

// Variable Declarations
let x, num, sum;

// Assign value to the variables
x = 20;
y = 30

// Expression to divide a number
num = x / 2;

// Expression to add two numbers
sum = x + y;

console.log(num + "\n" + sum);

10
50

JavaScript Keywords

The keywords are the reserved words that have special meanings in JavaScript. 

// let is the keyword used to
// define the variable
let a, b;

// function is the keyword which tells
// the browser to create a function
function GFG(){};

JavaScript Comments

The comments are ignored by the JavaScript compiler. It increases the readability of code. It adds suggestions, Information, and warning of code. Anything written after double slashes // (single-line comment) or between /* and */ (multi-line comment) is treated as a comment and ignored by the JavaScript compiler.

Example: This example shows the use of javascript comments.

// Variable Declarations
let x, num, sum;

// Assign value to the variables
x = 20;
y = 30

/* Expression to add two numbers */
sum = x + y;

console.log(sum);

50

JavaScript Data Types

JavaScript provides different datatypes to hold different values on variables. JavaScript is a dynamic programming language, which means do not need to specify the type of variable. There are two types of data types in JavaScript. 

• Primitive data type
• Non-primitive (reference) data type

// It store string data type
let txt = "GeeksforGeeks";

// It store integer data type
let a = 5;
let b = 5;

// It store Boolean data type
(a == b )

// To check Strictly (i.e. Whether the datatypes
// of both variables are same) === is used
(a === b)---> returns true to the console
 
// It store array data type
let places= ["GFG", "Computer", "Hello"];

// It store object data (objects are 
// represented in the below way mainly)
let Student = {
    firstName: "Johnny",
    lastName: "Diaz", 
    age: 35, 
    mark: "blueEYE"
}

JavaScript Functions

JavaScript functions are the blocks of code used to perform some particular operations. JavaScript function is executed when something calls it. It calls many times so the function is reusable.

Syntax: 

function functionName( par1, par2, ....., parn ) {  
    // Function code
}  

The JavaScript function can contain zero or more arguments.

Example: This example shows the use of Javascript functions.

// Function definition
function func() {

    // Declare a variable
    let num = 45;

    // Display the result
    console.log(num);
}

// Function call
func();

45

JavaScript Identifiers

JavaScript Identifiers are names used to name variables and keywords and functions.

A identifier must begin with:

• A letter(A-Z or a-z)
• A dollar sign($)
• A underscore(_)

Note: Numbers are not allowed as a first character in JavaScript Identifiers.

JavaScript Case Sensitive

JavaScript Identifiers are case-sensitive.

Example: Both the variables firstName and firstname are different from each other.

let firstName = "Geek";
let firstname = 100;

console.log(firstName);
console.log(firstname);

Geek
100

JavaScript Camel Case

In JavaScript Camel case is preferred to name a identifier.

Example:

let firstName
let lastName

JavaScript Character Set

A unicode character set is used in JavaScript. A unicode covers the characters, punctuations and symbols.

We have a complete article on character sets. Click here to read Charsets article.