How to compare two JavaScript array objects using jQuery/JavaScript?-JS Tutorial-php.cn

Home

Web Front-end

JS Tutorial

How to compare two JavaScript array objects using jQuery/JavaScript?

PHPz

Aug 22, 2023 pm 09:49 PM

How to compare two JavaScript array objects using jQuery/JavaScript?

In JavaScript, an array is an object with an index as a key and an array value as the value of a specific key of the array object. Sometimes, we need to check if two arrays are the same.

The first solution that comes to my mind is to use the equal sign operator to compare like array1 == array2. oops! This won't work because an array is an object and in JavaScript we can't compare two objects directly. So, we have to compare each element of the array.

In this tutorial, we will learn different methods to compare two JavaScript array objects.

Use the sort() method of JavaScript and compare every element

The sort() method allows us to sort array values in JavaScript. After that, we can use a for loop to compare the elements at each index in the array. If the elements at any index do not match, we can say that the two array objects are different.

Syntax

Users can use the sort() method and for loop to compare two array objects according to the following syntax.

// sort arrays first
arra1.sort();
array2.sort();
   if (array1.length != array2.length) {
      // arrays are not the same
   } else {
      for () {
         // if elements at index i are not the same, return false
      }
   }
}
// both arrays are the same

Algorithm

Users can operate according to the following algorithm.

Step 1 − Use the sort() method to sort both arrays.
Step 2 - Compare the lengths of the two arrays; if the lengths are not the same, return false, indicating that the two arrays are not the same.
Step 3 − If the lengths of the two arrays are the same, use a for loop to traverse the two arrays.
Step 4 − Compare the elements of both arrays at every index, and if the elements at the index don’t match, return false.
Step 5 - Two arrays are identical if all elements in both arrays match.

Example

In the following example, we create two arrays of numbers and sort them using the sort() method. We then use a for loop to compare each element of the two arrays.

In the output, users can see that both arrays are the same as both arrays contain the same values.

<html>
<body>
   <h3>Using the <i>array.sort()</i> method and <i>for</i> loop to check if two arrays are the same using JavaScript </h2>
   <button onclick = "checkArray()"> Compare arrays </button>
   <div id = "output"> </div>
   <script>
      let output = document.getElementById('output');
      let array1 = [32, 32, 54, 1, 2, 3, 4];
      let array2 = [1, 2, 3, 4, 32, 54, 32];
      output.innerHTML += "The first array values are " + array1 + "<br>";
      output.innerHTML += "The second array values are " + array2 + "<br>";
      function checkArray() {
         array1.sort();
         array2.sort();
         if (array1.length != array2.length) {
            output.innerHTML += "Both arrays are not same!";
            return false;
         } else {
            for (let i = 0; i < array1.length; i++) {
               if (array1[i] != array2[i]) {
                  output.innerHTML += "Both arrays are not same!";
                  return false;
               }
            }
         }
         output.innerHTML += "Both arrays are the same!";
         return true;
      }
   </script>
</body>
</html>

Use forEach loop and indexOf() method

We can use the forEach loop to iterate through every array element. The indexOf() method finds the first occurrence of the element in the array and returns -1 if the reference array doesn’t contain the element.

Syntax

Users can use the forEach loop and indexOf() method to compare two array objects according to the following syntax.

if (array2.length != array1.length) {
   // array are not the same
   return false;
} else {
   array1.forEach((element) => {
      if (array2.indexOf(element) == -1) {
         return false;
      }
   })
}

Algorithm

In this algorithm, we don’t need to sort the arrays like the first approach.

Step 1 - Check if the lengths of the two arrays are the same; if not, return false.
Step 2 − If the lengths are the same, use the forEach() loop to iterate through every element.
Step 3 − For each element of array 1, use the indexOf() method to check whether it exists in array 2.
Step 4 - If the indexOf() method returns -1 for any element, it means that the two arrays are not the same.

Example

In the example below, when the user clicks the button, it will invoke a compareArray() function. The compareArray() function compares the two arrays of string elements.

In the output, the user can observe that the two arrays are not the same because the values of the two arrays are different.

<html>
<body>
   <h3 id="Using-the-i-forEach-loop-and-indexOf-method-i-to-check-if-two-arrays-are-the-same-using-JavaScript">Using the <i>forEach() loop and indexOf() method</i> to check if two arrays are the same using JavaScript </h3>
   <button onclick = "compareArray()"> Compare arrays</button>
   <div id = "output"> </div>
   <script>
      let output = document.getElementById('output');
      let array1 = ["Hello", "Hi", "How"];
      let array2 = ["Are", "You", "!"];
      output.innerHTML += "The first array values are " + array1 + " <br>";
      output.innerHTML += "The second array values are " + array2 + " <br>";
      function compareArray() {
         var isSame = true;
         if (array2.length != array1.length) {
            output.innerHTML += "Both arrays are not same!";
            return false;
         } else {
            array2.forEach((element) => {
               if (array1.indexOf(element) == -1) {
                  isSame = false;
               }
            })
         }
         if (isSame) {
            output.innerHTML += "Both arrays are the same!";
         } else {
            output.innerHTML += "Both arrays are not same!";
         }
         return true;
      }
   </script>
</body>
</html>

We have learned two different ways to compare two arrays in JavaScript. Users can use the first method to compare arrays containing duplicate values, while the second method is only suitable for comparing arrays containing unique values.

Also, users can use the JSON.stringify() method to compare the array of objects and sorted arrays.

The above is the detailed content of How to compare two JavaScript array objects using jQuery/JavaScript?. For more information, please follow other related articles on the PHP Chinese website!

Statement

This article is reproduced at:tutorialspoint. If there is any infringement, please contact admin@php.cn delete

From Websites to Apps: The Diverse Applications of JavaScriptApr 22, 2025 am 12:02 AM

JavaScript is widely used in websites, mobile applications, desktop applications and server-side programming. 1) In website development, JavaScript operates DOM together with HTML and CSS to achieve dynamic effects and supports frameworks such as jQuery and React. 2) Through ReactNative and Ionic, JavaScript is used to develop cross-platform mobile applications. 3) The Electron framework enables JavaScript to build desktop applications. 4) Node.js allows JavaScript to run on the server side and supports high concurrent requests.

Python vs. JavaScript: Use Cases and Applications ComparedApr 21, 2025 am 12:01 AM

Python is more suitable for data science and automation, while JavaScript is more suitable for front-end and full-stack development. 1. Python performs well in data science and machine learning, using libraries such as NumPy and Pandas for data processing and modeling. 2. Python is concise and efficient in automation and scripting. 3. JavaScript is indispensable in front-end development and is used to build dynamic web pages and single-page applications. 4. JavaScript plays a role in back-end development through Node.js and supports full-stack development.

The Role of C/C in JavaScript Interpreters and CompilersApr 20, 2025 am 12:01 AM

C and C play a vital role in the JavaScript engine, mainly used to implement interpreters and JIT compilers. 1) C is used to parse JavaScript source code and generate an abstract syntax tree. 2) C is responsible for generating and executing bytecode. 3) C implements the JIT compiler, optimizes and compiles hot-spot code at runtime, and significantly improves the execution efficiency of JavaScript.

JavaScript in Action: Real-World Examples and ProjectsApr 19, 2025 am 12:13 AM

JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.

JavaScript and the Web: Core Functionality and Use CasesApr 18, 2025 am 12:19 AM

The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.

Understanding the JavaScript Engine: Implementation DetailsApr 17, 2025 am 12:05 AM

Understanding how JavaScript engine works internally is important to developers because it helps write more efficient code and understand performance bottlenecks and optimization strategies. 1) The engine's workflow includes three stages: parsing, compiling and execution; 2) During the execution process, the engine will perform dynamic optimization, such as inline cache and hidden classes; 3) Best practices include avoiding global variables, optimizing loops, using const and lets, and avoiding excessive use of closures.

Python vs. JavaScript: The Learning Curve and Ease of UseApr 16, 2025 am 12:12 AM

Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.

Python vs. JavaScript: Community, Libraries, and ResourcesApr 15, 2025 am 12:16 AM

Python and JavaScript have their own advantages and disadvantages in terms of community, libraries and resources. 1) The Python community is friendly and suitable for beginners, but the front-end development resources are not as rich as JavaScript. 2) Python is powerful in data science and machine learning libraries, while JavaScript is better in front-end development libraries and frameworks. 3) Both have rich learning resources, but Python is suitable for starting with official documents, while JavaScript is better with MDNWebDocs. The choice should be based on project needs and personal interests.

See all articles