Mastering DataWeave in MuleSoft: 100+ Practice Questions (Part 2)

Manoj Prabhakar Thakare

2 min read

·

Mar 19, 2026

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Question 11 — Convert Names to Uppercase

Input

["john","sam","alex"]

Expected Output

["JOHN","SAM","ALEX"]

DataWeave Logic

%dw 2.0
output application/json
---
payload map upper($)

Question 12 — Count Number of Elements

Input

[1,2,3,4,5]

Expected Output

5

DataWeave Logic

%dw 2.0
output application/json
---
sizeOf(payload)

Question 13 — Get First Element from Array

Input

[10,20,30]

Expected Output

10

DataWeave Logic

%dw 2.0
output application/json
---
payload[0]

Question 14 — Sort Numbers in Ascending Order

Input

[5,3,8,1]

Expected Output

[1,3,5,8]

DataWeave Logic

%dw 2.0
output application/json
---
payload orderBy $

Question 15 — Reverse an Array

Input

[1,2,3,4]

Expected Output

[4,3,2,1]

DataWeave Logic

%dw 2.0
output application/json
---
payload[-1 to 0]

Question 16 — Check if Array Contains a Value

Input

[1,2,3,4]

Expected Output

true

(Check if value 3 exists)

DataWeave Logic

%dw 2.0
output application/json
---
payload contains 3

Question 17 — Rename Keys in Object

Input

{
 "first_name":"John",
 "last_name":"Doe"
}

Expected Output

{
 "firstName":"John",
 "lastName":"Doe"
}

DataWeave Logic

%dw 2.0
output application/json
---
{
 firstName: payload.first_name,
 lastName: payload.last_name
}

Question 18 — Extract Unique Values

Input

[1,2,2,3,3,4]

Expected Output

[1,2,3,4]

DataWeave Logic

%dw 2.0
output application/json
---
payload distinctBy $

Question 19 — Group Objects by Field

Input

[
 {"name":"A","dept":"IT"},
 {"name":"B","dept":"HR"},
 {"name":"C","dept":"IT"}
]

Expected Output

{
 "IT":[
   {"name":"A","dept":"IT"},
   {"name":"C","dept":"IT"}
 ],
 "HR":[
   {"name":"B","dept":"HR"}
 ]
}

DataWeave Logic

%dw 2.0
output application/json
---
payload groupBy $.dept

Question 20 — Add New Field to Object

Input

{
 "name":"Manoj",
 "age":25
}

Expected Output

{
 "name":"Manoj",
 "age":25,
 "status":"active"
}

DataWeave Logic

%dw 2.0
output application/json
---
payload ++ {status:"active"}

🙌 Thanks for Reading

This is part of my ongoing DataWeave practice series.

If this helped you, feel free to connect with me on LinkedIn — I’d love to learn about your MuleSoft journey and share knowledge together.

Stay tuned for the next parts!

🔥 Happy Integrating!