I’m very new to JavaScript, and have recently learned about declaring variables with var. like var a = 12 or whatever. But, I came across a line in some code for a website I was reading through for fun which read var t={};. This was actually only the second line of code. I can’t seem to find any explanation online anywhere for what it means to set a variable to equal a set of empty curly braces. I thought it might be a way of declaring an array or something??

I’m very new to JavaScript, and have recently learned about declaring variables with var. like var a = 12 or whatever. But, I came across a line in some code for a website I was reading through for fun which read var t={};. This was actually only the second line of code. I can’t seem to find any explanation online anywhere for what it means to set a variable to equal a set of empty curly braces. I thought it might be a way of declaring an array or something??

• javascript
• variables
• var

• 3 {} is an empty object. – CertainPerformance Commented Oct 15, 2018 at 2:42

4 Answers 4

This defines a variable as an empty object

var t = {}

This defines it as an empty array

var t = []

This defines it as a boolean

var t = true

This defines it as an empty string

var t = ''

This defines it as an integer(number)

var t = 0

These are the basic building blocks/data types of javascript. There are plenty of tutorials online which cover this in the first lesson.

https://javascript.info/object

https://javascript.info/types

An object is a collection of data, it can contain arrays, booleans, strings, integers and even other objects. Objects consist of key/value pairs:

var user = { 
  // the key here is name and the value is a string 'Tom'
  name: 'Tom', 
  // the value can also be an integer
  age: 23,
  // or an array
  interests: ['gaming','travel','guitar'], 
  // or a boolean
  loggednIn: false,
  // or a nested object
  contact: { 
    email: '[email protected]',
    number: 01296714100
  }
}

var is one keyword from javascript language, used to define variable. Below is an explanation from Mozilla Developer Network (MDN):

The var statement declares a variable, optionally initializing it to a value

Statement var t={}; means a new variable called t defined with initialised value is {}. The {} is literal for empty object, more explanation.

TL;DR; empty object created, stored in newly created variable t.

It works to initialize an object.

For example, if you declare:

var a = {}

and get the type using typeof(a) you going to get object. Different to:

var b = 1 - typeof(b) is equals to number var c = foo - typeof(c) is equals to string

And as object you can declare more plex variables, like

var a = { 'stackoverflowName':'mrmins', 'url':'https://stackoverflow.', 'gender':'mygender'}

let user = new Object(); // "object constructor" syntax
let user = {};  // "object literal" syntax

Usually, the figure brackets {...} are used. That declaration is called an object literal.

Please go through the following article for more clarity https://javascript.info/object