How to Compare Arrays in Javascript?

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Several different approaches of compare two arrays in JavaScript are discussed in this article. Find out what type of comparison you want to make before settling on a method.

Do you want to make sure that they have the same values and are ordered the same way? Alternatively, you might check to see if the values in both arrays match. Both of these cases, and others, will be discussed more below.

Remember there are numerous methods to achieve this goal; choosing the right one depends on how much emphasis you place on easy-to-understand syntax and how much on speed.

How to Compare Arrays in Javascript?


Multiple cases of comparison, such as array crossings and differences, are addressed by the provided solutions.

Because of this, it may be required to fine-tune the solutions to increase speed when working with extremely large arrays.

How to Check If Two Arrays Are Identical?


One possible method of determining whether or not two arrays are equivalent is presented below. Thus, the values at the same positions in both arrays are identical.

let arrayOne = ['a','b','c','d']
let arrayTwo = ['a','b','c','d']

function isEqual(array1, array2) {
  if (array1.length !== array2.length) return false;
  return array1.every((value, index) => value === array2[index])
}

let result = isEqual(arrayOne, arrayTwo);

console.log(result)

//OUTPUT
//true

In this approach, we built a function to generalize our comparison logic. First, we verify whether or not the arrays are dissimilar in size.

That’s a quick but crucial check to make, as iterating the arrays would be pointless if we already knew they were different. Following this, we utilize every prototype to check each item in both arrays.

To perform a test on each member of the array, every function iterates through all of the elements in the array. Here, we’ll utilize the index to compare each array’s values to one another.

 

Use a Library LoDash _.isEqual

A library is a good option to consider if you need to create many different methods to manipulate arrays and other operations.

LoDash is a good choice since it includes a built-in method to determine whether or not two arrays are equivalent. The isEqual method is available after the LoDash library has been imported.

let arrayOne = ['a','b','c','d']
let arrayTwo = ['a','b','c','d']

let result = _.isEqual(arrayOne, arrayTwo)

console.log(result)

//OUTPUT
//true

 

Honorable Mention – JSON.Stringify


The arrays may be converted to strings and then the strings can be compared. The performance isn’t great, but at least our code is simpler with this technique.

Errors that result from inconsistencies between the numeric and string representations of some data might also arise and prove challenging to troubleshoot.

let arrayOne = ['a','b','c','d']
let arrayTwo = ['a','b','c','d']

function isEqual(array1, array2) {
  if (array1.length !== array2.length) return false;
	
  return JSON.stringify(array1) === JSON.stringify(array2);
}

let result = isEqual(arrayOne, arrayTwo)

console.log(result)

//OUTPUT
//true

 

How to Check If Two Arrays Have the Same Values?


Here’s how to determine if two arrays have the same elements, even if they aren’t arranged identically.

let arrayOne = ['a','b','c','d']
let arrayTwo = ['d','b','a','c']

function isEqual(array1, array2) {
	
  if (array1.length !== array2.length) return false;

  let matching = array1.filter(val => array2.includes(val))
    
  if (matching.length == array1.length) return true;
  
  return false    
}


let result = isEqual(arrayOne, arrayTwo);

console.log(result)

//OUTPUT
//true

Again, we check to see if the arrays are the same in size before doing any serious computation.

Then, we check if each value in the second array appears at a specific index by applying a filter operation on the first array and using the prototype provided therein.

If the length of the array returned by this filter operation is the same as the length of the array we fed into it, we know that the arrays we compared contain the same values.

 

How to Find Matching Values Between Two Arrays (Intersection)?


To find out where two arrays meet, follow these steps. The intersection operation compares two arrays and returns true if and only if each array contains the specified value.

let arrayOne = ['a','b','c','d']
let arrayTwo = ['a','b','3','4']

let intersection = arrayOne.filter(val => arrayTwo.includes(val))

console.log(intersection)

//OUTPUT
//["a","b"]

 

How to Find Values Not In Both Array (Difference)?


Learn how to determine the dissimilarity between two arrays by following these instructions. As the inverse of “intersection,” the difference is the logical opposite.

Those are all the elements in both arrays that are unique to themselves.

let arrayOne = ['a','b','c','d','e']
let arrayTwo = ['a','b','3','4']

let diffOne = arrayOne.filter(val => !arrayTwo.includes(val))
let diffTwo = arrayTwo.filter(val => !arrayOne.includes(val))
let difference = diffOne.concat(diffTwo)

console.log(difference)

//OUTPUT
//["c", "d", "e", "3", "4"]

There you have it. You now know how to compare arrays in Javascript.

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