Imagine having an object named x with values x = { a: 'abc', b: 'jkl' },
Next, I am assigning this object x to a new local variable y using var y = x.
Now, when the value of var y changes as y.a = 'pqr', y.b = 'xyz', the object var x is automatically updated with the new values { a: 'pqr', b: 'xyz' } from var y.
While this behavior is often desirable, there are cases where it needs to be prevented. How can this be achieved?
You can access the Plunker code for this here
To prevent the issue, you have two options:
Option 1 - Using Object.assign:
var x = { a: 'abc', b: 'jkl' }
var y = Object.assign({}, x);
y.a = 'modified';
console.log('x: ', x);
console.log('y: ', y);Option 2 - Using the Spread operator:
var x = { a: 'abc', b: 'jkl' }
var y = { ...x };
y.a = 'modified';
console.log('x: ', x);
console.log('y: ', y);In this particular situation, a new object is assigned to y while x remains unchanged.
If you were to modify some properties of either x or y, both references would point to the same updated object.
var x = { a: 'abc', b: 'jkl' };
y = x;
y = { a: 'pqr', b: 'xyz' };
console.log(x);
console.log(y);Greetings to all! A few weeks ago, I embarked on the journey of learning javascript, node.js and mongo. As a beginner, I have an interesting task at hand today. My goal is to add a simple document to the mongoDB and perform a conditional check. So here&apo ...
My form includes inline validation for a specific input field. <form name="coForm" novalidate> <div> <label>Transaction: </label> <input type="text" name="transaction" class="form-control" placeholder="<Dir ...
I am currently working on my website and I have been trying to add a button to the bottom of the page that can play or pause a song using useSound library. The song starts playing when I click it for the first time, however, I am facing difficulty in stopp ...
I'm new to exploring jade in conjunction with express.js and I'm on a quest to fully understand jade. Here's my query: Express mentions caching jade in production - but how exactly does this process unfold? Given that the output is continge ...
I need a quick way to check if a value is an object {} but not an array []. The code I currently have is: function isPlainObject(input) { return !Array.isArray(input) && typeof input === 'object'; } Is there a more concise method to a ...
Currently, I am facing an issue with retrieving links for PDFs from my Firebase storage and binding them to specific lists. The problem arises because the template is loaded before the links are fetched, resulting in the href attribute of the list remainin ...
Currently, I have a form that is submitted using PHP with three different submit actions: Save and Continue Save and Exit Exit without Saving The goal is to trigger an "OnBeforeUnload" alert if the user does not click on any of the form actions. This al ...
Recently, I've been working on creating a jest test for the function below that sets a sessionStorage entry: /** * @desc create authenticated user session * @param {String} [email=''] * @param {Date} [expires=Date.now()] * @param {St ...
Looking to implement drop-down options within a Flatlist component, I've utilized the React Native Popup Menu and declared MenuProvider as the entry point in App.tsx. Encountering the following error: Error: Type '{ children: Element[]; }' ...
Looking for a way to split a lengthy HTML text-only article into multiple divs for easier page navigation on mobile devices? Perhaps dividing it into separate pages that users can swipe through on their iPad or iPhone? I've experimented with JavaScri ...
I am encountering an issue with react-router and unable to render my app due to this error. Here is a screenshot of the error I have searched extensively for a solution but have not been able to find anything useful. Any help would be greatly appreciated ...
Apologies if the question is not well-formed, I am completely new to working with React. I have been attempting to create a dashboard but encountering issues with my states getting reinitialized. Below is the content of my app.js file. import './inde ...
I am currently working on a project within the freeCodeCamp "API and Microservices" curriculum that involves using Express.js to handle routes. The project itself is relatively straightforward, with some pre-defined routes and others that need to be creat ...
Currently attempting to construct my application with target: 'serverless' set in the next.config.js file (in order to deploy on AWS Lambda). Upon running npm run build, I am encountering the following output: Warning: Built-in CSS support is bei ...
I am facing a React.js task that involves sending a POST request to the server. I need to trigger this POST request when a user clicks on the submit button. However, I keep encountering two specific errors: App.js:19 POST http://localhost:3001/ net::ERR_CO ...
Whenever I build my site for the first time, the CSS breaks initially, but strangely fixes itself when I press command + s on the code. It seems like hot reloading does the trick here. During development, I can temporarily workaround this issue by making ...
Unique Context In my webpage, I have a specific div element with the CSS property of overflow: auto. Within this scrolling div, there is structured content like this: <h3>Group A</h3> <ul> <li>Item 1</li> <li>I ...
When using fabric js, I have successfully drawn various shapes like circles and rectangles. However, I encountered an issue while trying to obtain the coordinates of the rectangle using the fabric.rect() method. canvas.getActiveObject().get('points& ...
After struggling for a day with multiple failed attempts, I have been unsuccessful in converting a React Class Component. The original class component code is as follows: class NeonCursor extends React.Component { constructor(props) { super(props); ...
In my current project, I am utilizing React and Material UI to display a grid. The grid's rows are populated from an array of data, with each row containing specific information in columns structured like this: <Grid container> {myData.map((re ...