Basic Javascript Knowledge

Javascript was created by Brendan Eich in 1995. Its syntax is inherited from the Java and C languages.· Javascript is a

· multi-paradigm,

· dynamic language with types and operators,

· standard built-in objects, and methods,

· object-oriented programming with object prototypes, instead of classes,

· functional programming.

Javascript has no concept of input and output because it was designed as a scripting language to run in the host environment(browsers, Adobe Acrobat, Adobe Photoshop, SVG images, Yahoo’s Widget Engine, server-side environments such as Node js, NoSQL databases like the open-source Apache CouchDB, embedded computers, complete desktop environments like GNOME, and others.)

Types of Javascript:

• Number
• String
• Boolean
• Symbol (new in ES2015)
• Object
• Function
• Array
• Date
• RegExp
• null
• undefined

Let’s discuss Numbers, Strings:

Numbers:

The JavaScript Number type is a double-precision 64-bit binary format IEEE 754 value. Like double in Java or C#, It can only represent floating-point value, not an integer.

Syntax: Literal syntax and functional syntax are two kinds of syntax in Number.

420; //literal syntax

Number(420); // functional syntax ; Here Number() is a function ,It converts string or other types to Number types.

Create Number syntax: Number() //it creates a number.

Functions for Number:

IsNaN(): IsNaN determines that the value is a number or not by printing True or False

Example:

IsNaN(2) ; // True

IsNaN(hello); // False

parseInt(): parseInt converts a string or binary to an integer. It takes two arguments- one is passed value and the other is the base for the value.

Example:

parseInt(‘567’,10); // 567 ;converting string to integer.

parseInt(‘110’,2); // 5 ;converting binary to integer.

parseFloat(): parseFloat takes an argument and converts a string to a floating-point value.

Example:

parseFloat(‘12.3’);//12.3

Math: Math is a built-in object, not a function object that has static properties and methods for mathematical constants and functions.

Example:

Math.abs(2) ; // 2; returns absolute value.

Math.ceil(4.3); // 5; returns the smallest integer greater than or equal to value.

Math.floor(4.3); // 4 ;returns the largest integer less than or equal to value.

Math.min(2,5,6);// 2 ; returns the smallest of zero or more numbers.

Math.max(2,5,6); // 6 ; returns the largest of zero or more numbers.

Math.random() ; // returns a pseudo-random number between 0 and 1.

Math.round(6.89) ; // 7 ; returns the value of the number value rounded to the nearest integer.

Math.sqrt(4); // 16 ; returns the positive square root of value.

Strings:

Strings are used to represent formatted text including characters, integers, and the floating-point unit, sequences of Unicode characters.

Syntax: String literals can be specified using single or double quotes, which are treated identically, or using the backtick character.

data_type variable_name = “ variable_value”;

data_type variable_name = ‘ variable_name’;

data_type variable_name = ` variable_name`;

Example:

const string1 = “ Hello World”;

const string2 = ‘Hello World’;

const string3 =` Hello World`;

Methods for Strings:

charAt(): charAT () accesses information about the string.

Example: ‘Bob’,charAt(1); // ‘o’

lastIndexOf(): lastIndexOf() method returns the index of string of the last occurrence of the specified value, searching backwards from from index. Returns -1 if the value is not found.

Example:

const string1 = ‘ this is a pen’;

const n = string1.lastIndexOf(‘s’); // 6