JavaScript: Find the unique elements from two arrays

JavaScript Array: Exercise-42 with Solution

Unique Elements from Two Arrays

Write a JavaScript function to find unique elements in two arrays.

Test Data :
console.log(difference([1, 2, 3], [100, 2, 1, 10]));
["1", "2", "3", "10", "100"]
console.log(difference([1, 2, 3, 4, 5], [1, [2], [3, [[4]]],[5,6]]));
["1", "2", "3", "4", "5", "6"]
console.log(difference([1, 2, 3], [100, 2, 1, 10]));
["1", "2", "3", "10", "100"]

Visual Presentation:

Sample Solution:

JavaScript Code :

// Function to find the difference between two arrays
function difference(arr1, arr2) {
  // Flatten the input arrays using the 'flatten' function
  var a1 = flatten(arr1, true);
  var a2 = flatten(arr2, true);

  var a = [], diff = [];
  
  // Initialize a dictionary 'a' with values from 'a1' and set them to false
  for (var i = 0; i < a1.length; i++)
    a[a1[i]] = false;
  
  // Iterate through 'a2' and update the dictionary values
  for (i = 0; i < a2.length; i++)
    if (a[a2[i]] === true) {
      delete a[a2[i]];
    } else {
      a[a2[i]] = true;
    }

  // Extract keys from the dictionary 'a' and push them to the 'diff' array
  for (var k in a)
    diff.push(k);
  
  // Return the array containing the differences
  return diff;
}

// Function to flatten an array (recursive)
var flatten = function(a, shallow, r) {
  // If 'r' is not provided, initialize it as an empty array
  if (!r) {
    r = [];
  }
  
  // Check if shallow flattening is requested
  if (shallow) {
    // Use 'concat' to flatten the array
    return r.concat.apply(r, a);
  }

  // Iterate through the array and recursively flatten nested arrays
  for (var i = 0; i < a.length; i++) {
    if (a[i].constructor == Array) {
      flatten(a[i], shallow, r);
    } else {
      r.push(a[i]);
    }
  }

  // Return the flattened array
  return r;
};

// Output the result of the 'difference' function with sample arrays
console.log(difference([1, 2, 3], [100, 2, 1, 10]));
console.log(difference([1, 2, 3, 4, 5], [1, [2], [3, [[4]]],[5,6]]));
console.log(difference([1, 2, 3], [100, 2, 1, 10]));

Output:

["1","2","3","10","100"]
["1","2","3","4","5","6"]
["1","2","3","10","100"]

Flowchart :

ES6 Version:

// Function to find the difference between two arrays
function difference(arr1, arr2) {
  // Flatten the input arrays using the 'flatten' function
  const a1 = flatten(arr1, true);
  const a2 = flatten(arr2, true);

  const a = [];
  const diff = [];
  
  // Initialize a dictionary 'a' with values from 'a1' and set them to false
  for (let i = 0; i < a1.length; i++)
    a[a1[i]] = false;
  
  // Iterate through 'a2' and update the dictionary values
  for (let i = 0; i < a2.length; i++)
    if (a[a2[i]] === true) {
      delete a[a2[i]];
    } else {
      a[a2[i]] = true;
    }

  // Extract keys from the dictionary 'a' and push them to the 'diff' array
  for (const k in a)
    diff.push(k);
  
  // Return the array containing the differences
  return diff;
}

// Function to flatten an array (recursive)
const flatten = (a, shallow, r) => {
  // If 'r' is not provided, initialize it as an empty array
  if (!r) {
    r = [];
  }
  
  // Check if shallow flattening is requested
  if (shallow) {
    // Use 'concat' to flatten the array
    return r.concat(...a);
  }

  // Iterate through the array and recursively flatten nested arrays
  for (let i = 0; i < a.length; i++) {
    if (Array.isArray(a[i])) {
      flatten(a[i], shallow, r);
    } else {
      r.push(a[i]);
    }
  }

  // Return the flattened array
  return r;
};

// Output the result of the 'difference' function with sample arrays
console.log(difference([1, 2, 3], [100, 2, 1, 10]));
console.log(difference([1, 2, 3, 4, 5], [1, [2], [3, [[4]]],[5,6]]));
console.log(difference([1, 2, 3], [100, 2, 1, 10]));

Live Demo :

See the Pen JavaScript -Find the unique elements from two arrays-array-ex- 42 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that finds elements unique to each of two arrays and returns their union without duplicates.
• Write a JavaScript function that uses Set operations to determine unique elements present in either array.
• Write a JavaScript function that manually compares two arrays and extracts elements that are not common to both.
• Write a JavaScript function that handles arrays with mixed data types and returns the unique elements from both arrays.

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• JavaScript array Exercises Home ↩
• JavaScript Exercises Home ↩

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