Styled-components is a CSS-in-JS library that enables you to write regular CSS and attach it to JavaScript components. With styled-components, you can use the CSS you’re already familiar with instead of having to learn a new styling structure.
Utilising tagged template literals (a recent addition to JavaScript) and the power of CSS, styled-components allows you to write actual CSS code to style your components.
React and ReactDOM are two distinct libraries that are commonly used together in the development of web applications with React.
React is a JavaScript library focused on building user interfaces. It follows a declarative approach, where developers define what the UI should look like based on the current state of the application. React then efficiently updates and renders components as the state changes. Its design emphasizes flexibility and efficiency, making it a popular choice for developing both web and mobile applications.
ReactDOM, on the other hand, serves as a bridge between React and the DOM (Document Object Model). The DOM is a hierarchical structure representing the HTML content of a web page. ReactDOM provides a set of methods that enable React components to be rendered and updated within the DOM. It ensures that the user interface is synchronized with the underlying HTML structure.
In summary, React is a library for building user interfaces, while ReactDOM handles the interaction with the DOM, rendering React components onto the web page. Although they are often used together, they serve different purposes and can function independently of each other.
Your components will often need to display different things depending on different conditions. In React, you can conditionally render JSX using JavaScript syntax like if statements, &&, and ? : operators.
&& operator
{ isYes && <A />}
? : operator
isYes ? Yes() : No()
{cond ? <A /> : <B />} means “if cond, render <A />, otherwise <B />.{cond && <A />} means “if cond, render <A />, otherwise nothing”.Lifting state up in react means moving data from a child component to some parent component either to use it there or pass it some other child component.
There are many default browser actions:
mousedown – starts the selection (move the mouse to select).click on <input type="checkbox"> – checks/unchecks the input.submit – clicking an <input type="submit"> or hitting Enter inside a form field causes this event to happen, and the browser submits the form after it.keydown – pressing a key may lead to adding a character into a field, or other actions.
contextmenu – the event happens on a right-click, the action is to show the browser context menu.All the default actions can be prevented if we want to handle the event exclusively by JavaScript.
To prevent a default action – use either event.preventDefault() or return false. The second method works only for handlers assigned with on<event>.
The passive: true option of addEventListener tells the browser that the action is not going to be prevented. That’s useful for some mobile events, like touchstart and touchmove, to tell the browser that it should not wait for all handlers to finish before scrolling.
If the default action was prevented, the value of event.defaultPrevented becomes true, otherwise it’s false.
A component with its own local state is often referred to as uncontrolled.
In contrast, a component is considered controlled when its key data and behavior are managed externally through props, rather than relying on its own local state. This approach allows the parent component to have full control over its behavior and data flow.
When designing a component, carefully consider which pieces of information should be controlled (managed via props) and which should remain uncontrolled (handled by the component’s state). However, keep in mind that you’re not locked into your initial decision—you can always refactor later as the needs of your application evolve.
A module is just a file. One script is one module. As simple as that.
import/export work, browsers need <script type="module">.When we use modules, each module implements the functionality and exports it. Then we use import to directly import it where it’s needed. The browser loads and evaluates the scripts automatically.
In production, people often use bundlers such as Webpack to bundle modules together for performance and other reasons.
The TIMESTAMP datatype is an extension on the DATE datatype. In addition to the datetime elements of the DATE datatype, the TIMESTAMP datatype holds fractions of a second to a precision between zero and nine decimal places, the default being six. There are also two variants called TIMESTAMP WITH TIME ZONE and TIMESTAMP WITH LOCAL TIME ZONE. As their names imply, these timestamps also store time zone offset information.
create table table_name (
column_name number,
column_name2 timestamp default systimestamp);
Material UI uses Emotion as its default styling engine.
Run the following commands to add Material UI to your project:
npm install @mui/material @emotion/react @emotion/styled
Emotion Emotion is a library designed for writing css styles with JavaScript. It provides powerful and predictable style composition in addition to a great developer experience with features such as source maps, labels, and testing utilities. Both string and object styles are supported.
There are two primary methods of using Emotion. The first is framework agnostic and the second is for use with React.
styled is a way to create React components that have styles attached to them. It’s available from @emotion/styled. styled was heavily inspired by styled-components and glamorous.
import styled from '@emotion/styled'
const Button = styled.button`
padding: 32px;
background-color: hotpink;
font-size: 24px;
border-radius: 4px;
color: black;
font-weight: bold;
&:hover {
color: white;
}
`
render(<Button>This my button component.</Button>)
Syntax error
The error occurs when you use a predefined syntax incorrectly.
Reference Error
In a case where a variable reference can’t be found or hasn’t been declared, then a Reference error occurs.
Type Error
An error occurs when a value is used outside the scope of its data type.
RangeError
There is an error when a range of expected values is required
URI Error
When the wrong character(s) are used in a URI function, the error is called.
InternalError
This error occurs internally in the JS engine, especially when it has too much data to handle and the stack grows way over its critical limit.
Evaluation Error
Current JavaScript engines and EcmaScript specifications do not throw this error. However, it is still available for backward compatibility. The error is called when the eval() backward function is used.