DATA TYPES Java Script has many data types

DATA TYPES

ü Java Script has many data types: Numbers, Strings, Objects, etc. E. g: var length=16; //Number var name=“Johnson”; //String var x={firstname: ”John”, lastname: ”son”}; //Object ü A computer cannot safely solve expressions without data types. E. g: var x = 16 + “Volvo”; var x = 16 + 4 + “Volvo”; var x = “Volvo” + 16 + 4;

ü Java Script data types are dynamic data types i. e same variable can be used to hold different data types. E. g: var x; //Now x is undefined var x=5; //Now x is a number var x=“John”; //Now x is a string

ü The different data types in Java script are: (i) String (ii) Number (iii) Boolean (iv) Object (v) Undefined (vi) Function

(i) String: üA string (or a text string) is a series of characters. üStrings are written with quotes. You can use single or double quotes: E. g: var x = "John"; // Using double quotes var x = ’John’; // Usingle quotes

ü You can use quotes inside a string, as long as they don't match the quotes surrounding the string: E. g: var answer = "It's alright"; // Single quote inside double quotes var answer = "He is called 'Johnny' "; // Single quotes inside double quotes var answer = 'He is called "Johnny" '; // Double quotes inside single quotes var s= “John” son”; //error *********************************** E. g: var x = “John”; typeof x; //Returns String ***********************************

üAn empty value has nothing to do with undefined. üAn empty string has both a legal value and a type. E. g: var car = ""; // The value is "", the typeof is "string"

(ii) Number: üJava. Script has only one type of numbers. üNumbers can be written with, or without decimals: E. g: var x 1 = 34. 00; // Written with decimals var x 2 = 34; // Written without decimals üExtra large or extra small numbers can be written with scientific (exponential) notation: E. g: var y = 123 e 5; // 12300000 var z = 123 e-5; // 0. 00123

(iii) Boolean: üBooleans can only have two values: true or false. *********************** E. g: var x = true; typeof x; //Returns Boolean ***********************

(iv) Object: üIn Java. Script, arrays are treated as Objects. E. g: var names = [“john", “ravi", “sai"]; typeof names; //Returns Object üJava. Script objects are written with curly braces. üObject properties are written as name : value pairs, separated by commas. E. g: var person = {first. Name : "John", last. Name : "Doe", age : 50, eye. Color : "blue"}; typeof person; //returns Object

üIn Java. Script null is "nothing". It is supposed to be something that doesn't exist. üUnfortunately, in Java. Script, the data type of null is an object. E. g 1: var person = {first. Name: "John", last. Name: "Doe", age: 50, eye. Color: "blue"}; person = null; // Now value is null, but type is still an object E. g 2: var a=null; //value is null typeof a; // data type is Object

(v) Undefined: üIn Java. Script, a variable without a value, has the value undefined. E. g: var a; // Value is undefined, type is undefined üAny variable can be emptied, by setting the value to undefined. The type will also be undefined. E. g var a=10; a = undefined; // Value is undefined, type is undefined

üYou can also empty an object by setting it to undefined: E. g: var person = {first. Name: "John", last. Name: "Doe", age: 50, eye. Color: "blue"}; person = undefined; // Now both value and type is undefined Difference Between Undefined and Null üUndefined and null are equal in value but different in type: E. g: typeof undefined // undefined typeof null // object

(vi) Function: typeof function my. Func(){} // Returns "function"