How Can I Efficiently Find the Differences Between Two JavaScript Object Arrays?

Finding the Difference Between Two Object Arrays in JavaScript

In JavaScript, you may encounter the need to determine the difference between two arrays of objects. For instance, you might have two result sets that you want to compare and identify the objects that only exist in one but not the other.

To achieve this, you can leverage a combination of native JS functions and a custom comparison function. Here's how you can do it:

1. Define a Comparison Function:

   const isSameUser = (a, b) => a.value === b.value && a.display === b.display;

This function will determine whether two objects are equal based on their 'value' and 'display' properties.

2. Use the 'onlyInLeft' Function:

   const onlyInLeft = (left, right, compareFunction) => 
     left.filter(leftValue =>
    !right.some(rightValue => 
      compareFunction(leftValue, rightValue)));

This function takes three arguments: the left array, the right array, and the comparison function. It filters out the elements from the left array that do not have corresponding elements in the right array based on the defined comparison function.

3. Use the 'onlyInLeft' Function to Find Differences:

   const onlyInA = onlyInLeft(a, b, isSameUser);
   const onlyInB = onlyInLeft(b, a, isSameUser);

This code applies the 'onlyInLeft' function to the two arrays, using the comparison function to determine the differences.

4. Create the Final Result:

   const result = [...onlyInA, ...onlyInB];

Finally, the 'result' array contains the objects that are present in one array but not in the other.

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