# Type Conversion and Coercion in javascript


## Type Conversion


![Untitled (12).jpg](https://cdn.hashnode.com/res/hashnode/image/upload/v1638710069384/xIdsleqtLO.jpeg)

**Explicit Conversion**

Converting one data type to another manually. This is done using some built-in methods. Except for null and undefined, all primitive values have object equivalents that wrap around the primitive values. Values of one types can be converted to other type using these functions.

![Untitled (14).jpg](https://cdn.hashnode.com/res/hashnode/image/upload/v1638770431642/AE3XPLMBe.jpeg)

Let's have a look at the ways to convert one type to another.

### 1. Conversion to Number

**a.)  Number()**
Number is a primitive wrapper object used to represent and manipulate numbers. It converts other types values to numbers using Number() function. 

```
Number('30')  //30
Number('30') === 30  // true
Number('')//0
const d=new Date('August 30, 1999')
console.log(Number(d)) //935951400000
``` 
If the value can't be converted, it returns NaN.

```
Number("Ishita")  // NaN
Number(undefined) //NaN
``` 

If we pass the boolean value, then

```
Number(true) // 1
Number(false) // 0

``` 

**b.) Using parseInt()**

parseInt() is used to convert a string to number. It takes two parameters, the string to be parsed and the radix to be used. A radix parameter specifies the number system to use:

2 = binary
8 = octal
10 = decimal
16 = hexadecimal


*parseInt(string, radix)*

If radix param is not used the JavaScript assumes radix 10. If the value begins with "0x", JavaScript assumes radix 16.


```
parseInt("10", 10) //10
parseInt("120", 8) //80
parseInt("20", 16) //32
parseInt("") // NaN
``` 

> 
**parseInt() parses up to the first non-digit unlike number which convert the entire string into a number**

```
parseInt('123ab') //123
Number('123ab') //NaN

``` 
### 2. Conversion to String

**a.) String()**

The String object is used to represent and manipulate a sequence of characters. It converts other types values  to strings  using String() function.


```
String(45) //'45'
String(undefined) //'undefined'

```
** b.) toString()**

The toString() method converts a number to a string. It also takes radix as parameter.

```
let num = 30;
num.toString();  //'30'
num.toString(2) //'11110'
``` 
> 
toString() will cause an error if value is null or undefined while String() do not cause any error.


```
String(null) //'null'
String(undefined)//'undefined'
let str=null
str.toString() // TypeError
``` 

### 3. Conversion to Boolean

Boolean object converts other types values  to boolean  using Boolean() function. If the value is undenied, NaN, 0, ''(with no space),null, it will be considered as false. 


```
Boolean(NaN) //false
Boolean(undefined) //false
Boolean(0) //false
Boolean('') //false
Boolean(null)//false
``` 


> 
Point to remember: An empty string with spaces, empty object and array return true.


```
Boolean(' ') //true
Boolean([]) //true
Boolean({}) //true
``` 
All other values than this gives true (conditions not included here)


```
Boolean('hey')   //true
Boolean("false")  //true
Boolean(23)  //true
``` 

## Type Coercion

![Untitled (18).jpg](https://cdn.hashnode.com/res/hashnode/image/upload/v1638790369087/jf-xST_pu.jpeg)

Just like in this image string itself fall into the waterfall of integer , type coercion works in the same way. Type coercion automatically convert values of one type to another type rather than manually doing it.

### 1. Type coercion of numbers to string

The + operator used for addition, can also be used to concatenate strings. It automatically converts numbers to string. For example,

```
console.log('I am ' + 5 + ' years old')
``` 
In this case  5 being an integer automatically converts into string without using any built-in function. This is called an **implicit conversion** .

Now it's play time. 
   
GUESS THE OUTPUT GAME?????????

```
console.log(1+2+3+'4')
console.log('1' +2+3+4)
``` 
Hope you guessed the right output, to check the solution, press cmd+option+J if you are on Mac or ctrl+shift+J(on Windows/Linux). It will open up the console. Paste the code over there and see the answer.

### 2. Type coercion of string to numbers

 / ,-, * operators automatically convert string to numbers.  


```
console.log('30'-'10') //20
console.log('30'-'10'+ '3') //203
console.log('30'+'10'- '3') //3007
console.log('10' * '2') //20
console.log('10'/'2') //5
``` 
AGAIN READY FOR GUESS THE OUTPUT GAME?????????

```
let num= 1+2+'3'+4;
num=num/2;
num=num-(50+50+100-'33');
console.log(Boolean(num))
``` 

That's all about it. If you have some question then feel free to  message me on linkedIn or Twitter.
LinkedIn: https://www.linkedin.com/in/ishitarastogii/
Twitter: https://twitter.com/Ishita_30