What s the difference between and while declaring a JavaScript array

Question

What   s the difference between          and          while declaring a JavaScript array  Normally I declare like  var a       What is the meaning of declaring the array as var a

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- this is used whenever we are declaring an empty array      - this is used whenever we declare an empty object typeof        object  typeof        object  but if your run     constructor name    Array  so from this  you will understand it is an array here Array is the name of the base class  The JavaScript Array class is a global object that is used in the construction of arrays which are high-level  list-like objects

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var a         it is use for brackets for an array of simple values  eg   var name   a   b   c    var a      is use for value arrays and objects properties also  eg   var programmer      name   special    url   www google com

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In JavaScript Arrays and Objects are actually very similar  although on the outside they can look a bit different   For an array   var array       array 0     hello   array 1    5498  array 536    new Date      As you can see arrays in JavaScript can be sparse  valid indicies don t have to be consecutive  and they can contain any type of variable  That s pretty convenient   But as we all know JavaScript is strange  so here are some weird bits   array  0        hello      This is true array  hi       undefined array  hi      weird      works but does not save any data to array array  hi       still undefined    This is because everything in JavaScript is an Object  which is why you can also create an array using new Array     As a result every index in an array is turned into a string and then stored in an object  so an array is just an object that doesn t allow anyone to store anything with a key that isn t a positive integer   So what are Objects   Objects in JavaScript are just like arrays but the  index  can be any string   var object       object 0     hello      OK object  hi      not weird      OK   You can even opt to not use the square brackets when working with objects   console log object hi      Prints  not weird  object hi    overwriting  not weird      You can go even further and define objects like so   var newObject         a  2     newObject a     2     true

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Nobody seems to be explaining the difference between an array and an object      is declaring an array      is declaring an object   An array has all the features of an object with additional features  you can think of an array like a sub-class of an object  where additional methods and capabilities are added in the Array sub-class   In fact  typeof         object  to further show you that an array is an object   The additional features consist of a magic  length property that keeps track of the number of items in the array and a whole slew of methods for operating on the array such as  push     pop     slice     splice    etc     You can see a list of array methods here   An object gives you the ability to associate a property name with a value as in   var x       x foo   3  x  whatever     10  console log x foo           shows 3 console log x whatever      shows 10   Object properties can be accessed either via the x foo syntax or via the array-like syntax x  foo     The advantage of the latter syntax is that you can use a variable as the property name like x myvar  and using the latter syntax  you can use property names that contain characters that Javascript won t allow in the x foo syntax   A property name can be any string value     An array is an object so it has all the same capabilities of an object plus a bunch of additional features for managing an ordered  sequential list of numbered indexes starting from 0 and going up to some length   Arrays are typically used for an ordered list of items that are accessed by numerical index   And  because the array is ordered  there are lots of useful features to manage the order of the list  sort   or to add or remove things from the list

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When you declare   var a       you are declaring a empty array   But when you are declaring  var a       you are declaring a Object    Although Array is also Object in Javascript but it is numeric key paired values  Which have all the functionality of object but Added some few method of Array like Push Splice Length and so on   So if you want Some values where you need to use numeric keys use Array  else use object   you can Create object like   var a  name  abc  age  14       And can access values like  console log a name

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they are two different things       is declaring an Array  given  a list of elements held by numeric index      is declaring a new object  given  an object with fields with Names and type value  some like to think of it as  Associative Array   but are not arrays  in their representation   You can read more   This Article

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It can be understood like this   var a        creates a new empty array var a        creates a new empty object   You can also understand that  var a       is equivalent to var a  new Object     Note   You can use Arrays when you are bothered about the order of elements of same type  in your collection else you can use objects  In objects the order is not guaranteed

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Syntax of JSON   object          members     members   pair   pair  members   pair   string   value   array          elements     elements   value   value elements   value   string number object array true false null

[javascript] What’s the difference between “{}” and “[]” while declaring a JavaScript array?

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