Data Type Converstion

1. Implicit Type Conversion (Type Coercion)

JavaScript automatically converts data types in some operations.

Expression	Converted To	Result
"5" + 3	String	"53" (String concatenation)
"5" - 3	Number	2 (Subtraction forces number conversion)
true + 2	Number	3 (true → 1)
false + 2	Number	2 (false → 0)
5 + null	Number	5 (null → 0)
"5" * "2"	Number	10 (Multiplication forces number conversion)
"5" == 5	Boolean	true (loose equality converts "5" to number)

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2. Explicit Type Conversion (Manual Conversion)

You can manually convert values using JavaScript methods.

String Conversion

Method	Example	Result
String()	String(123)	"123"
toString()	(123).toString()	"123"

Number Conversion

Method	Example	Result
Number()	Number("123")	123
parseInt()	parseInt("123px")	123 (Extracts number from string)
parseFloat()	parseFloat("12.34px")	12.34

Boolean Conversion

Method	Example	Result
Boolean()	Boolean(1)	true
!!value	!!0	false

Truthy and Falsy Values in Boolean Conversion

• Falsy Values (convert to false): 0, "" (empty string), null, undefined, NaN, false
• Truthy Values (convert to true): All other values, including "0", "false", [], {}, function(){}

3. Special Cases in Type Conversion

Expression	Converted To	Result
Number(undefined)	NaN	NaN
Number(null)	0	0
Number(true)	1	1
Number(false)	0	0
Number(" 123 ")	123	123 (Trims spaces)
Number("abc")	NaN	NaN
Boolean("false")	true	"false" is a non-empty string
Boolean([])	true	An empty array is truthy
Boolean({})	true	An empty object is truthy

4. JSON Conversion

To convert objects or arrays to JSON strings:

const obj = { name: "Rahul", age: 25 };
console.log(JSON.stringify(obj)); // '{"name":"Rahul","age":25}'

To convert a JSON string back to an object:

const jsonString = '{"name":"Rahul","age":25}';
console.log(JSON.parse(jsonString)); // { name: "Rahul", age: 25 }