Saturday 16 March 2024

In data weave, how do you merge two arrays?149

 In data weave, how do you merge two arrays?

DataWeave offers a couple of effective ways to merge two arrays into a single array:

Method 1: Using the Spread Operator (...)

The spread operator (...) allows you to efficiently combine elements from multiple arrays:

%dw 2.0
// Sample arrays
var array1 = [1, 2, 3];
var array2 = ["apple", "banana", "cherry"];

// Merge the arrays using spread operator
output = [...array1, ...array2];


  • The spread operator unpacks the elements of each array within the square brackets.

  • The result is a single array containing all elements from both array1 and array2.

Method 2: Using the concat Function

The concat function provides another approach for array concatenation:

%dw 2.0
// Sample arrays (same as previous example)
output = array1 concat array2;


  • The concat function takes two arrays as arguments and returns a new array containing the combined elements.

Choosing the Right Method:

  • Both methods achieve the same outcome.

  • The spread operator might be considered more concise and readable, especially for simple merges.

  • The concat function offers a more explicit approach and can be useful when dealing with functions or variables holding the arrays you want to merge.

Additional Considerations:

  • You can merge more than two arrays by adding them within the square brackets for the spread operator or using multiple arguments with concat.

  • DataWeave preserves the order of elements during the merge operation.

Example with Duplicates:

If the arrays might contain duplicate elements, both methods will result in a merged array where duplicates are preserved. Here's an example:

%dw 2.0
var array1 = [1, 2, 3];
var array2 = [2, 3, 4];

output = [...array1, ...array2]; // output: [1, 2, 3, 2, 3, 4]

Removing Duplicates (Optional):

To create a unique set of elements after merging, you can leverage the distinctBy function:

%dw 2.0
output = [...array1, ...array2] distinctBy $;  // output: [1, 2, 3, 4]

This approach uses distinctBy $ to remove duplicates based on the element itself ($).

By understanding these methods, you can effectively merge arrays in your DataWeave transformations within MuleSoft applications.

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