javascript

JavaScript Arrays

JavaScript arrays are written with square brackets.

Array items are separated by commas.

The following code declares (creates) an array called cars, containing three items (car names): Example var cars = ["Saab", "Volvo", "BMW"];

JavaScript Objects

JavaScript objects are written with curly braces {}.

Object properties are written as name:value pairs, separated by commas. Example var person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"};

typeof something

In JavaScript null is "nothing". It is supposed to be something that doesn't exist.

Unfortunately, in JavaScript, the data type of null is an object.

You can consider it a bug in JavaScript that typeof null is an object. It should be null. You can empty an object by setting it to null: Example var person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"}; person = null; // Now value is null, but type is still an object

You can also empty an object by setting it to undefined: Example var person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"}; person = undefined; // Now both value and type is undefined

undefined and null are equal in value but different in type: typeof undefined / undefined typeof null / object

null = undefined / false null == undefined / true

A primitive data value is a single simple data value with no additional properties and methods.

The typeof operator can return one of these primitive types:

string number boolean undefined

The typeof operator can return one of two complex types:

function object

The typeof operator returns "object" for objects, arrays, and null.

The typeof operator does not return "object" for functions.

• Math.ceil — округляет все в большую сторону,
• Math.floor — в меньшую,
• Math.round — меньше 0.5 — в меньшую, больше 0.5 — в большую.

function getRandomInRange(min, max) {
       return Math.floor(Math.random() * (max - min + 1)) + min;
   }

console.log(getRandomInRange(0, 9))

Using toString()

toString(base) function converts a given a number to the string. It takes an optional parameter base which can be used to specify the base in which the number will be represented as a string.

It works for floating point and exponential numbers also.

let num = 15;
num.toString(); //"15"
num.toString(2); //"1111" (binary)
num.toString(8); //"17"   (octa)
num.toString(16); //"f"   (hexa)

num = 15.55;
num.toString(); //"15.55"

num = 15e10;
num.toString(); //"150000000000"

By concatenating with empty string ""

This the most simplest method which can be used to convert a int to string in javascript.

As javascript is loosely typed language when we concatenate a number with string it converts the number to string.

15 + '' // "15";
15.55 + '' // "15.55";
15e10 + '' // "150000000000"

As you can see we can also convert floating point and exponential numbers.