Javascript Syntax

Javascript syntax is the set of rules that dictate how programs written in Javascript should be structured.

Variables and Declarations:

Declare variables using let, const, or var:

Example:

// 'variable' declaration using let keyword.
let age = 20;

// 'variable' declaration using const keyword.
const name = 'Alice';

// 'variable' declaration using var keyword.
var count = 10;  // 'var' is older and has some difference in scoping

Data Types:

Javascript has several built-in data types, including numbers, strings, booleans, objects, arrays, and more.

Integer:

'num' variable storing integer value.

let num = 12;

String:

'text' variable storing string value.

let text = 'Hello World, javascript!';

Boolean:

'flag' variable storing boolean value.

let flag = false;

Object:

The 'personObj' variable storing the object as the value.

let personObj = { name: 'Alice', age: 20 };

Array:

'colors' variable storing array as value.

let colors = ['red', 'green', 'blue'];

function as value:

'functionName' variable storing function as the value.

let functionName = function() { /* function body can be added inside curly braces */ };

Operators:

Arithmetic, comparison, logical, and assignment operators are used for various operations:

Subtract Operator

Subtract Operator, storing difference of two values.

let difference = 12 - 10;

Addition Operator

Addition Operator, storing the sum of two values.

let sum = 12 + 7;

Assignment Operator For Increment

Assignment Operator decrement value by 1.

let decrement = sum--;

Assignment Operator For Decrement

Assignment Operator Increment value by 1.

let increment = sum ++;

Comparison Operator

let isGreaterThan = 10 > 5;

Logical Operator

let logicalAnd = true && false;

Control Structures:

Javascript supports conditional statements (if-else), loops (for, while, do-while), switch-case and more.

if else statements

if (x > 10) {
  // code block
} else {
  // code block
}

for loop statements

for (let i = 0; i < 10; i++) {
  // code block
}

while loop statements

while (x < 10) {
  // code block
  x += 1;
}

Objects:

Objects are collections of key-value pairs. It can hold any type of value.

Example:

let employee = {
  name: "Alice",
  age: 23,
  isStudent: false
};

Classes:

Javascript supports class-based object-oriented programming after classes introduced in ES6.

Example:

class Employee {
  constructor(name, age, isStudent) {
    this.name = name;
    this.age = age;
    this.isStudent = isStudent;
  }

}

// Creating instance of Employee class to access properties and behaviour
let employee = new Employee("Alice", 23, false);
console.log(employee.name, employee.age);

<-- Home