JavaScript Tutorial

JavaScript

• console.time();

• console.timeEnd();

• console.table();

• console.clear();

• console.error();

• console.assert();

console.assert(12 < 11 "true");

Variables and Data Types

Rules of defining Variables:

• Variables can not start with numbers.

• Variable can start with the letter, underscore("_").

• Note: JavaScript is a case-sensitive language.

Most common programming case type:

• camelCase

• Kebab-case

• snake_case

• PascalCase

Data Types

• Primitive data type

• Reference data type

Primitive data type: 

• The primitive data type is known as the Built-in data type in JavaScript.

• The memory location of primitive data type in a stack.

• base

Examples:

• String

• numbers

• Boolean

• Null

• undefined

• symbol (ES6 classes)

Reference data type

• The primitive data type is known as the User-defined data type in JavaScript.

• The memory location of reference data type in a Heap.

• Object

Examples:

• Array

• Object literals (like dictionary)

• functions

• dates

Type conversation

Code snippet:

let a = String(45);

//OR

//a = '45';

console.log(a);

//To find the type of the variable

console.log(typeof a);

//Is use to convert the variable into a string

console.log(a.toString());

let a = 45;

let b = a.toString();

console.log(typeof a);

console.log(typeof b);

let a = Number("45");

// a = Number("45fgjhf");

let b = a.toString();

console.log(typeof a);

console.log(typeof b);

console.log(a, b);

let a = Number(true);

let b = a.toString();

console.log(typeof a, a);

console.log(typeof b, b);

let a = parseInt('45');

console.log(typeof a);

console.log(a);

//convert onto integer

let a = parseInt('45.4567');

console.log(typeof a);

console.log(a);

//Convert into float

let a = parseFloat('45.4567');

console.log(typeof a);

console.log(a);

//Is use to fix the decimal zero position

console.log(a.toFixed());

console.log(a);

//Is use to fix the decimal second position

console.log(a.toFixed(2));

console.log(a);

//concatination

console.log("3"+2);

Comments

Example:

//This is singel line comment

/*

This is multiline comment

*/

 Strings

Strings are useful for holding data that can be represented in text form.

• Properties, Methods, and Template Literals:

String Methods:

• startsWith():

• endsWith():

• includes():

• split():

• length()

• slice()

• substring()

• substr()

• replace()

• replaceAll()

• toUpperCase()

• toLowerCase()

• concat()

• trim()

• trimStart()

• trimEnd()

• padStart()

• padEnd()

• charAt()

• charCodeAt()

• indexOf()

• lastIndexOf()

• search()

• match()

• matchAll()

String  Literals:

let text = "Hello world!";