JavaScript_course

Data types

In JavaScript there are six data types:

Five of them are described as primitive data types.
The sixth is the object (and is referred to as a complex data type).

Key	Value type
String	“JavaScript is awesome!!”
Number	1,2,2.5,…
Boolean	true, false
Undefined	Undefined
Null	null
Object	{}

Whenever you have a value that is a string, you can use the properties and methods of the String object on that valu e. This example stores the phrase “Home sweet home “ in a variable.

let saying = "Home sweet home ";

When you declare a variable in JavaScript, It will be wrapped under the hood with objects according to the type of the variable. In our example we define a string and for that javaScript wrap the variable with special methods that we can use. The properties & methods are:

Properties

Property	Description
`length`	Returns number of characters in the string in most cases (see note bottom-left)

Methods

Property	Description
`toUpperCase()`	Changes string to uppercase characters
`toLowerCase()`	Changes string to lowercase characters
`charAt()`	Takes an index number as a parameter, and returns the character found at that position
`indexOf()`	Returns index number of the first time a character or set of characters is found within the string
`lastIndexOf()`	Returns index number of the last time a character or set of characters is found within the string
`substring()`	Returns characters found between two index numbers where the character for the first index number is included and the character for the last index number is not included
`split()`	When a character is specified, it splits the string each time it is found, then stores each individual part in an array
`trim()`	Removes whitespace from start and end of string
`replace()`	Like find and replace, it takes one value that should be found, and another to replace it (by default, it only replaces the first match it finds)

Each character in a string is automatically given a number, called an index number. Index numbers always start at zero and not one (just like for items in an array).

String methods `

References and Terms:

:gem: Read more about Data type structure in JavaScript