# DataWeave : mapObject()

## mapObject()  :  

It transforms an Object to a new Object.
mapObject is used when we want to change the keys and/or values on an Object to be a different object.

It does this by iterating over each key/value pair in the object and applying a transformation to each key and value. The result of the transformation is collected together and output as an object.


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Note : An Object starts with { and end with } and inside it has key-value pairs or nil
```


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Note : Whenever we are applying mapObject function other than the Objects, we get the exception
``` 


**mapObject(Object<Key,Value>, (Value,Key,index) -> Object): Object **

** Value(default $):  ** it represents the value part of a key-value pair  in an object

** Example : **  
![ex1.PNG](https://cdn.hashnode.com/res/hashnode/image/upload/v1646635040102/kMzpBDEO6.PNG)

In the above image  ** James Peter  ** belongs to ** Value(default $)** part 

** Example : ** 
![ex2.PNG](https://cdn.hashnode.com/res/hashnode/image/upload/v1646635675350/Eghlhpb0W.PNG)

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** Key(default $$) :** it represents the key part of a key-value pair  in an object
** Example : ** 
![ex3.PNG](https://cdn.hashnode.com/res/hashnode/image/upload/v1646635956688/n0CE0pM3L.PNG)

In the above image  ** name  ** belongs to ** Key(default $$)** part 

![ex4.PNG](https://cdn.hashnode.com/res/hashnode/image/upload/v1646637062596/JkPTvpd_ci.PNG)

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** index(default $$$) :** it represents the position part of a key-value pair  in an object

** Example : **

![ex5.PNG](https://cdn.hashnode.com/res/hashnode/image/upload/v1646637079543/3ejpTgscr.PNG)

** Example : **



![ex6.PNG](https://cdn.hashnode.com/res/hashnode/image/upload/v1646638256495/hM-caEak7.PNG)

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** Exception case: **

Here we got an error while applying mapObject on an Array


![ex7.PNG](https://cdn.hashnode.com/res/hashnode/image/upload/v1646638400792/ngNbFTMib.PNG)



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