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JavaScript: Compute the union of two arrays

JavaScript Array: Exercise-22 with Solution

Write a JavaScript program to compute the union of two arrays.

Sample Data:
console.log(union([1, 2, 3], [100, 2, 1, 10]));
[1, 2, 3, 10, 100]

Pictorial Presentation:

JavaScript: Compute the union of two arrays

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>JS Bin</title>
</head>
<body>
</body>
</html>

JavaScript Code:

function union(arra1, arra2) {
  
  if ((arra1 == null) || (arra2==null)) 
    return void 0;
  
  var obj = {};
 
  for (var i = arra1.length-1; i >= 0; -- i)
     obj[arra1[i]] = arra1[i];
 
  for (var i = arra2.length-1; i >= 0; -- i)
     obj[arra2[i]] = arra2[i];
 
  var res = [];
 
  for (var n in obj)
  {
  
    if (obj.hasOwnProperty(n)) 
      res.push(obj[n]);
  }
 
  return res;
}
console.log(union([1, 2, 3], [100, 2, 1, 10]));

Sample Output:

[1,2,3,10,100]

Flowchart:

Flowchart: JavaScript : Compute the union of two arrays

ES6 Version:

function union(arra1, arra2) {
  
  if ((arra1 == null) || (arra2==null)) 
    return void 0;
  
  const obj = {};
 
  for (var i = arra1.length-1; i >= 0; -- i)
     obj[arra1[i]] = arra1[i];
 
  for (var i = arra2.length-1; i >= 0; -- i)
     obj[arra2[i]] = arra2[i];
 
  const res = [];
 
  for (const n in obj)
  {
  
    if (obj.hasOwnProperty(n)) 
      res.push(obj[n]);
  }
 
  return res;
}
console.log(union([1, 2, 3], [100, 2, 1, 10]));

Live Demo:

See the Pen JavaScript - Compute the union of two arrays - array-ex- 22 by w3resource (@w3resource) on CodePen.


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Next: Write a JavaScript function to find the difference of two arrays.

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04