JavaScript Built-in Classes and Their Useful Methods

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In this article, we intent to give you a list of built-in classes from JavaScript and their useful methods.

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You can click on each one of them to understand how those methods work.

Array Class

You can create an array using following constructor.

var myArray = new Array(23,44,5.5,'tomato');
console.log(myArray);
//Output = [23,44, 5.5,'tomato']

Popular Methods

• push()
• pop()
• shift()
• unshift()
• sort()
• join()
• slice()
• splice()

Number Class

This class converts string to numbers, and some other conversions. It uses the constructor called Number();

The Number constructor takes a number of type string and then convert into a number of type number.

var num = Number('34.5');
//typeof '34.5' is string.
console.log(num);
//output = 34.5 and typeof 34.5 is Number.

Popular Methods: Number Class

• parseInt()
• parseFloat()
• num.toFixed()
• num.toPrecision()
• num.toString()
• num.toExponential()

String Class

The string class has the constructor called String that used to create string objects.

Remember that it is different from the regular declaration of a string. For example

var name = "Spiderman";
var myFriend = new String('Ganesh');
console.log(typeof name); //output = String
console.log(typeof myFriend); //output = Object

Popular Methods: String Class

• toUpperCase()
• toLowerCase()
• indexOf()
• charAt()
• lastIndexOf()
• slice()
• substring()
• join()
• split()

Math Class

The math class has no constructors to create math object. However, it has many useful constants and functions that can be used in mathematical expressions.

Math Constants

Math.PI;
3.141592653589793 
Math.SQRT2;
1.4142135623730951 
Math.E; // Euler constant
2.718281828459045 
Math.LN2; // Neperian log of 2
0.6931471805599453 
Math.LN10; // Neperian log of 10
2.302585092994046

Popular Math Functions

• Math.random()
• Math.min(a, b) or Math.max(a,b)
• Math.round()
• Math.ceil()
• Math.floor()
• Math.pow()
• Math.sqrt()

Trigonometric Functions

• sin()
• cos()
• tan()
• atan()
• atan2(dy,dx)

Date Class

The date class has a constructor that returns current date. You can change the format of the dates using this parameters.

var date = new Date();
console.log(date.toString());
//output= "Tue Nov 05 2019 23:10:35 GMT+0530 (India //Standard Time)"

Useful Method of Date Class

• Date() // constructor returns current date and time
• date.getDay()
• date.getMonth()
• date.getHours()
• date.getFullYear()
• date.getMinutes()
• date.getSeconds()
• date.getTime()
• date.getMilliseconds()

All of the above methods have an equivalent set method.

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