Named 'container' for a piece of computer memory that holds a specified value.


  • Variable names consist of letters, number, _, $
  • Cannot start with a number


Variables are declared by using the keyword var followed by the desired name. e.g.

var name ; //declaration of a variable, undefined


Variables with no value are Undefined.



Values can also be assigned to a variable (aka initialisation) using the = assignment operator:

var age = 42 ; //definition of a variable


Variables can also be emptied by assigning them to a value of null. e.g.  myCar = null;



Multiple variables can be separated with commas: var firstName, middleName, lastName ;


Which can also be multiply initiated at definition: var firstName = "Alan", middleName = "Mathison", lastName = "Turing" ;


JavaScript does NOT require the data type being specified.


var myNumber = 200 ; //integer

var myFloat = 3.14 ; //floating point number


Text strings needs to be quoted with single or double quotes but should not be mixed at start/end. However, a single quote could be used within a double quoted string as an apostrophe:


var mySeason = "It's Spring again." ; //double quotes used around a string of text characters. Note use of single quote allowed with double quotes

var myWeather = 'My favourite weather is rainy!' ; //single quotes used around a string of text characters

var myBool = true ; //a boolean could also be assigned false

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