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 ↩
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