JS DataTypes

• JS Keywords/Reserve Words :

  • These words cannot be used as JavaScript variables, functions, methods, loop labels, or any object names by the programmers in their programs.
  • A list of all the reserved words in JavaScript are –

abstract, boolean, break, byte, case, catch, char, class, const, continue, debugger, default, delete, do, double, else, enum, export, extends, false, final, finally, float, for, function, goto, if, implements, import, in, Instanceof, int, interface, long, native, new, null, package, private, protected, public, return, short, static, super, switch, synchronized, this, throw, throws, transient, true, try, typeof, var, void, volatile, while, with.

• JS Data Type :

  • Data types are very important in Java script(JS) because JS has rich data type and provides different data types to hold different data values easily.
  • Dynamic Data Type:
    • Datatypes in JavaScript is of dynamic nature i.e. the nature of variable depends on the value assigned into it or same variable can be used to hold different data types.
    • JavaScript is a dynamic type language, i.e. we don’t need to specify the data type of the variable initially because it is dynamically configured by JavaScript engine automatically.
    • The var/let keyword is used to specify the dynamic data type.
    • Dynamic data type can hold any data type values.
    • For example:
      var a=40; // Here a stores numeric values hence a is number type.  
      var b=“India”; //Here b stores string values hence b is string type.  
  • Broadly the Java Script datatype is divided into two data types – 

(A) Primitive data type and (B) Non-primitive (reference) data type

(A) Primitive Data Type

There are five types of primitive data types in JavaScript:-

(A) Number

• • • The number data type holds any type of number, either an integer value or a real/float number. 
    • Examples : 

• • • This data type represents whole numbers larger than 2^53 – 1, which is the largest number that can be represented by the Number data type.

(C) String

• • • A string is a collection of a sequence of characters i.e. letters, digits, punctuation characters, symbols, or a combination of all these. 
    • Strings are declared within single or double quotes.
    • Examples : 

(D) Boolean

• • • A boolean variable can store only two possible values either true or false.
    • This data type represents a logical entity that can have one of two values: true or false.
    • Internally it is stored as 1 for true and 0 for false.

(E) Undefined

• • • This data type represents a variable that has been declared/used in the program but not exists or a variable that does not assign a value or a property that does not exist.

(F) Null

• • • This data type represents an intentional absence of any object value.
    • JavaScript supports a special data type known as null that indicates ‘no value at all or blank but may be in future’.
    • Null is not equal to 0 or empty.
    • For example :
      • var x= new object();
        x= null;

(G) Symbol

• • • This data type represents a unique identifier.

(B) Non-Primitive Data Type

(a) Object

• • • An object is a collection of properties, where each property has a name and a value.
    • Objects can contain any type of data, including other objects.
    • All variables in JavaScript are considered as object data types.

(b) Array

• • • An ordered collection of values, accessed by their index.

(c) RegExp

• • • This data type represents a regular expression.