React Force Re-render: Complete Guide
What Re-render is in React?
React performance can be worried about in two major phases:
Initial render: The first time a component appears on the screen is referred to as a first render.
Re-render: the second and later renders of existing displayed component.
A re-render occurs when React must re-render the application with new data. This normally arises when a user is manipulating the application, or when something external is being fed into it by asynchronous request or by a subscription facility.
Non interactive applications that do not update data asynchronously will never re-render so optimization of re-render speed is not required.
What is a Necessary and Unnecessary Re-render?
Necessary Re-rendering: It is re-rendering a component directly related to the changes or directly re-rendering the newly used information. As an example, the state controlling component must re-render itself each time a user types in an input field by making a keystroke.
Unnecessary Re-rendering: An unnecessary re-rendering is re-rendering a component that is interspersed throughout the application by different re-rendering mechanisms due to an error or ineffective architecture of the application. As an example, the page has rendered unnecessarily when the user type-ins a value in an input field and the entire page is re-rendered with every keystroke.
Unnecessary re-renders are not by themselves a problem since React is extraordinarily fast and can normally cope with them without the users noticing.
The user experience might however seem lagged, delays might be deliberate on each interaction or the app could just stop responding when re-renders are too frequent and/or on very large components.
What is Force Re-rendering?
In React force re-rendering is like clicking the refresh button on a page when it seems that everything is all right. It refers to telling an element in React to change and re-render itself, even when the data (stat/props) it consumes has not changed much.
Although React is typically good at deciding when a component is out of date, sometimes you wish to assume control and ask it to re-render a particular part of the code base. In this essay we will expound more on this.
Understanding How React Renders
Now we would like to take a closer look at the default rendering process in React. To understand when and why you may need to promote re-rendering, you would have to learn the internal architecture of React.
React is all about the magic of rendering with the help of the Virtual DOM. Imagine that it is a working duplicate of the real DOM, or structure of your webpage. React will consider what must be different when your data is updated based on this Virtual DOM. It is like practicing with a model house before you start painting on the one you intend to paint.
Then, how does React know when to update the Virtual DOM and change the webpage where necessary?
There are three steps to this:
Render Phase: The initial step, React decides which parts of your component’s user interface need to change as data changes. It detects the differences between the Virtual old and new DOM.
Reconciliation: React identifies the best way of updating the real DOM in cases where the differences between the two have been detected. This reconciliation process saves unnecessary work since only the aspects that saw an alteration in the data are modified.
Commit step: React also applies the calculated changes from the prior step to the real DOM in this final step. It is like you’re rubbing your paintbrush on the house and putting your fresh colors on the walls.
These phases need to be understood because they enlighten the default rendering behavior of React. Besides, they also assist us in deciding when and how force re-rendering should be used as necessary. In the sections that follow we will dive into when you might want to drive React through these phases and ensure that your components are in check with what your application state is.
Why do React Components Not Re-render?
Though React does not automatically update the components, it is not usually a good idea to force a React component to re-render. Since React counts on us to be good hosts, we ought to look at our code prior to considering enforcing a re-render.
Incorrectly Updated State in React
In order to explain a typical reason component are not rendering, we will create a simple component. We will develop the simplest application that shows the username Juan, and alters it to Peter when you press a button.
The following is one application of the entire code. Nothing happens when we click the Change user name button even after we updated our state on the button:
function changeUserName() {
user.name = “Peter”;
setUser(user);
}
Re-rendering trigger did not occur since the component was not changed. Why?
To decide whether the preview and the new value reference the same object, React updates state by evaluating them on shallow equality, also called reference equality. We technically setUser to the same object reference in our example, but we have mutated one of the properties of the user object, so React did not see any change in its state.
The React documentation states that state is supposed to be considered immutable. How can we fix it, then? We might create a new object such as the following one with the appropriate values:
function changeUserName() {
setUser({
…user,
name: “Peter”
});
}
Note that we are changing the name property of the original object under a new object and retaining its properties by using the spread operator of JavaScript. This is the result in its definitive form.
Incorrectly Updated Props Without State Change
It may not be at all apparent that one can update props in the wrong way without altering the state, but this normally causes problems. We shall take an example.
So, now we see the code which calculates the present time:
let myTime;
function setMyTime() {
myTime = new Date();
setTimeout(() => {
setMyTime();
}, 1000);
}
setMyTime();
Even though this is not the optimal approach to writing code to a React component and it is ugly, it gets the job done. Our Clock component receives the myTime variable to be rendered when the runtime invokes the setMyTime function each time it needs to update it on a one-second time interval:
<Clock myTime={myTime} />
The state is reflected in props, and hence simply altering them will not re-render them hence this example does not work. We should have to rewrite it entirely to get it straight.
As you will observe we added state to manage myTime and useEffect to stop and cancel the timers to avoid problems when the component re-renders. And it’s effective:
const [myTime, setMyTime] = useState(new Date());
useEffect(() => {
var timerID = setInterval(() => tick(), 1000);
return () => clearInterval(timerID);
});
function tick() {
setMyTime(new Date());
}
How To Implement Force Re-render in React?
React offers several ways of re-rendering a component. Next, we will explore ways to apply force re-renders in React.
Prerequisites
To implement the force react renderer successfully, you must have the following:
- js: The latest version of Node.json your machine.
- A Code Editor: Any IDE that supports React.
- React Library: The latest version of React on your machine.
Update the State
React allows you to change the state of a component to cause a re-render. Here is a sample piece of code:
import React, { useState } from ‘react’;
function Counter() {
const [count, setCount] = useState(0);
function increment() {
setCount(count + 1);
}
function forceRerender() {
setCount(count);
}
return (
<div>
<p>Count: {count}</p>
<button onClick={increment}>Increment</button>
<button onClick={forceRerender}>Force Rerender</button>
</div>
);
}
Here we have two buttons and a Counter component, which renders the count value. The increment function alters the count state by adding 1. The forceRerender functionality basically does nothing as it alters the value to the number at hand with the count state being updated as well. Since the state has changed, react will re-render the component and change the count value, however.
Use forceUpdate Method
The forceUpdate method that can be called on class components is another way of necessitating a re-render in react. Here is a sample piece of code:
import React, { Component } from ‘react’;
class MyComponent extends Component {
constructor(props) {
super(props);
this.state = { count: 0 };
}
increment() {
this.setState({ count: this.state.count + 1 });
}
forceRerender() {
this.forceUpdate();
}
render() {
return (
<div>
<p>Count: {this.state.count}</p>
<button onClick={() => this.increment()}>Increment</button>
<button onClick={() => this.forceRerender()}>Force Rerender</button>
</div>
);
}
}
Two buttons and a count value are also rendered by the MyComponent class component presented in this example. Incremental function increases the count state by adding 1. The forceRerender function calls forceUpdate in order to force a re-render of the component. Since it may lead to unnecessary re-renders and may not be as efficient as state change, this should be applied sparingly.
Change the Key Prop of a Component
Also, changing a key prop of a component can result in React re-rendering. React uses an exclusive feature known as the key prop to identify the list elements and to optimize updates.
Here is example code that demonstrates how changing the key prop of a child component could invoke a re-render:
import React, { useState } from ‘react’;
function List() {
const [items, setItems] = useState([‘apple’, ‘banana’, ‘cherry’]);
function shuffleItems() {
const shuffled = […items].sort(() => Math.random() – 0.5);
setItems(shuffled);
}
return (
<div>
<button onClick={shuffleItems}>Shuffle Items</button>
<ul>
{items.map((item, index) => (
<li key={item}>{item}</li>
))}
</ul>
</div>
);
}
The example has a List component which produces a list of items and a button to randomly shuffle the items. The list will be re-rendered when the order of the items in it changes since the key prop of an item is the value of the item itself.
When invoked, the shuffleItems function shuffles the current array creating a new array of items. List component is re-rendered when the new array is assigned as the state and React understands that the key prop of every item has been modified. The list is updated after reaction in accordance with the new order of the items.
Although the data in a component may be modified but the state remains the same, it may be useful to update the key prop to re-render. It is to be used sparingly, however, because the tendency to change the key prop can oftentimes lead to unnecessary re-renders and poor performance.
When Should You Avoid Force Rerendering in React?
When React automatically renders components when they are not required you may feel like pressing the refresh button, you just cannot act in a hurry on that. Making a component render without consideration will have plenty of ill effects even though you might not actually realize it. These consequences include:
Overloading The Reconciliation Process: When you overwork render burdensome to the process of reconciliation, you will need to do a great deal of needless work. Think of force rendering like you are painting your house every day. Doesn’t that make no sense? Excessive React Force Render has the same effect.
Side Effects: Force rendering a component in React may have a small number of unforeseen side effects. An example of unexpected effects includes data inconsistencies and bugs within user interface (UI).
Severe Debugging Issues: In case the side effects associated with force rendering are not sufficient to make you white-collar by night, the debugging issues that the overuse of this feature suddenly causes will surely send you nightmares. Indicatively, the last thing you want to do, when trying to solve a problem with a React SPA, is to deal with the extra complication of force-rendering a component at any given moment.
Disrupting Optimization of the Rendering Process: React is smartly optimizing the rendering process. To save work, it just updates what is needed. This optimization is however violated by the rerender forced by a rerender.
What You Need to Consider Before Performing React Force Rerender
React will be harmed when you render impulsively. This lack of constraint has two impacts on performance, namely, reduced performance and high resource use. That’s not all, though. When your overuse of react can cause the basic working of React to fail, it may crash down.
You may use an alternative structure, such as Vue vs. React, as a temporary solution, however, that should not be your top choice. Rather, you need to hire React JS developers that understand how to apply React Force Rerender prudently and timely. Reputable React JS development services will make use of React Force Rerenders as per their guidelines and rules.
The usage of force rerenders may sometimes be completely banned by developers, and sometimes they may be authorized only to specific use-case situations. It is also advisable that react JS developers should only resort to force rendering whereby there is a fundamental issue in the codebase which must be resolved.
Suppose that the force render is absolutely unavoidable. The developers that are working on the React application should in such scenario force render the component they are intending to update with the most optimal mechanism at their disposal.