React rewriting class with hooks causes re-render loops - reactjs

I am working on an image transition react component, where it waits to have img1 loaded and then on a user click loads the img2, but fades img1 smoothly.
Tried re-writing the application with hooks to set the states - but when this is applied it creates an re-render loop error.
Is it because we are always setting img1 as currentImgSrc initially?
const [imgSrcOne, setImgSrcOne] = useState(currentImgSrc)
errors in the if/else block? or is setting the useState in the return causing the bug
tried removing the if/else block to make the application functional
https://jsfiddle.net/b531L6ho/
import {
ImageTransition
} from './imageTransition/imageTranition'
const {
useState
} = React
interface ImageContainerProps {
layer: string
currentImgSrc: string
notifyOnError: (url: string) => void
updateLayerLoading: (hasLoaded: boolean) = void
}
export const ImageTransitionContainer: React.SFC < ImageContainerProps > = ({
currentImgSrc,
layer,
notifyOnError,
updateLayerLoading
}) => {
const [imgSrcOne, setImgSrcOne] = useState(currentImgSrc)
const [displayImgOne, setdisplayImgOne] = useState(true)
const [imgOneLoaded, setImgOneLoaded] = useState(false)
const [imgSrcTwo, setImgSrcTwo] = useState(currentImgSrc)
const [displayImgTwo, setdisplayImgTwo] = useState(true)
const [imgTwoLoaded, setImgTwoLoaded] = useState(false)
if (imgSrcOne && currentImgSrc !== imgSrcOne) {
console.log("in the if statement")
setImgSrcTwo(currentImgSrc)
setDisplayImgTwo(two)
}
if (currentImgSrc !== imgSrcOne) {
setImgSrcne(currentImgSrc)
}
if (!imgSrcOne && !imgSrcTwo) {
setImgSrcOne(currentImgSrc)
setDisplayImgOne(true)
} else if (imgSrcOne && currentImgSrc !== imgSrcOne) {
setImgSrcTwo(currentImgSrc)
setDisplayImgTwo(true)
} else if (imgSrcTwo && currentImgSrc !== imgSrcTwo) {
setImgSrcOne(currentImgSrc)
setDisplayImgOne(true)
}
console.log("state --", imgSrcOne, displayImgOne, imgOneLoaded, imgSrcTwo, displayImgTwo, imgTwoLoaded)
return (
<>
<ImageTransition
displayImg={displayImgOne}
imgLoaded={imgOneLoaded}
imgSrc={imgSrcOne}
onExit={() => {
setImgSrcOne(null)
setImgOneLoaded(false)
}}
onLoad={() => {
setImgOneLoaded(true)
setDisplayImgTwo(false)
}}
/>
<ImageTransition
displayImg={displayImgTwo}
imgLoaded={imgTwoLoaded}
imgSrc={imgSrcTwo}
onExit={() => {
setImgSrcTwo(null)
setImgTwoLoaded(false)
}}
onLoad={() => {
setImgTwoLoaded(true)
setDisplayImgOne(false)
}}
/>
</>
)
}

Related

React Typewriter effect doesn't reset

I have created a typewriting effect with React and it works perfectly fine. However, when I change the language with i18n both texts don't have the same length and it keeps writing until both texts have the same length and then it changes the language and starts the effect again.
How can I reset the input when the language has changed? How can I reset the input when the component has been destroyed?
I have recorded a video
I have the same issue when I change from one page to another, as both pages have different texts and they don't have the same length.
Here code of my component
export const ConsoleText = ({text, complete = false}) => {
const [currentText, setCurrentText] = useState("");
const translatedText = i18n.t(text);
const index = useRef(0);
useEffect(() => {
if (!complete && currentText.length !== translatedText.length) {
const timeOut = setTimeout(() => {
setCurrentText((value) => value + translatedText.charAt(index.current));
index.current++;
}, 20);
return () => {
clearTimeout(timeOut);
}
} else {
setCurrentText(translatedText);
}
}, [translatedText, currentText, complete]);
return (
<p className="console-text">
{currentText}
</p>
);
};
You are telling react to do setCurrentText(translatedText) only when it is complete or when the compared text lengths are equal, so yes it continues to write until this moment.
To reset your text when text changes, try creating another useEffect that will reset your states :
useEffect(() => {
index.current = 0;
setCurrentText('');
}, [text]);
Now, I actually did this exact same feature few days ago, here is my component if it can help you :
import React from 'react';
import DOMPurify from 'dompurify';
import './text-writer.scss';
interface ITextWriterState {
writtenText: string,
index: number;
}
const TextWriter = ({ text, speed }: { text: string, speed: number }) => {
const initialState = { writtenText: '', index: 0 };
const sanitizer = DOMPurify.sanitize;
const [state, setState] = React.useState<ITextWriterState>(initialState);
React.useEffect(() => {
if (state.index < text.length - 1) {
const animKey = setInterval(() => {
setState(state => {
if (state.index > text.length - 1) {
clearInterval(animKey);
return { ...state };
}
return {
writtenText: state.writtenText + text[state.index],
index: state.index + 1
};
});
}, speed);
return () => clearInterval(animKey);
}
}, []);
// Reset the state when the text is changed (Language change)
React.useEffect(() => {
if (text.length > 0) {
setState(initialState);
}
}, [text])
return <div className="text-writer-component"><span className="text" dangerouslySetInnerHTML={{ __html: sanitizer(state.writtenText) }} /></div>
}
export default TextWriter;
The translation is made outside of the component so you can pass any kind of text to the component.

Added isCancelled flag in useEffect, but still getting "Can't perform a React state update on an unmounted component..."

I created follow button component which cause a problem. It displays singularly on a tag page. On first load there is no error, but when I'm clicking other tag to display other tag's page then this error appears:
Can't perform a React state update on an unmounted component. This is a no-op, but it indicates a memory leak in your application. To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.
in FollowButton (at TagPage.tsx:79)
All answers I found on the internet says about adding isCancelled flag in useEffect hook, which I did, but it didn't help at all.
import React, { useEffect, useState, useContext } from "react";
import { Button } from "react-bootstrap";
import { FaRegEye } from "react-icons/fa";
import { useTranslation } from "react-i18next";
import FollowInfo from "../models/dtos/read/FollowInfo";
import UsersService from "../services/UsersService";
import Viewer from "../models/Viewer";
import { ViewerContext } from "../ViewerContext";
interface Props {
for: "user" | "tag";
withId: number;
}
const FollowButton = (props: Props) => {
//todo too much rerenders, button actually blinks at start and show wrong state
const { t } = useTranslation();
const [followInfo, setFollowInfo] = useState<FollowInfo | null>(null);
const [isSubmitting, setIsSubmitting] = useState(false);
console.log("follow rerender", followInfo);
let viewer: Viewer = useContext(ViewerContext);
useEffect(() => {
let isCancelled = false;
!isCancelled && setFollowInfo(null);
const fetchData = async () => {
if (props.for === "user") {
!isCancelled &&
setFollowInfo(
await UsersService.amIFollowingUser(
props.withId,
viewer.currentUser?.token
)
);
} else {
!isCancelled &&
setFollowInfo(
await UsersService.amIFollowingTag(
props.withId,
viewer.currentUser?.token
)
);
}
};
!isCancelled && fetchData();
return () => {
isCancelled = true;
};
}, [props, viewer.currentUser]);
const follow = (what: "tag" | "user", withId: number) => {
if (what === "user") {
followUser(withId);
} else {
followTag(withId);
}
setFollowInfo((state) => {
if (state != null) {
return { ...state, doesFollow: true };
} else {
return { receiveNotifications: false, doesFollow: true };
}
});
};
const unfollow = (what: "tag" | "user", withId: number) => {
if (what === "user") {
unfollowUser(withId);
} else {
unfollowTag(withId);
}
setFollowInfo((state) => {
if (state != null) {
return { ...state, doesFollow: false };
} else {
return { receiveNotifications: false, doesFollow: false };
}
});
};
const followUser = (userId: number) =>
makeRequest(() =>
UsersService.followUser(userId, viewer.currentUser?.token)
);
const unfollowUser = (userId: number) =>
makeRequest(() =>
UsersService.unfollowUser(userId, viewer.currentUser?.token)
);
const followTag = (tagId: number) =>
makeRequest(() => UsersService.followTag(tagId, viewer.currentUser?.token));
const unfollowTag = (tagId: number) =>
makeRequest(() =>
UsersService.unfollowTag(tagId, viewer.currentUser?.token)
);
const makeRequest = (call: () => Promise<any>) => {
setIsSubmitting(true);
call().then(() => setIsSubmitting(false));
};
return (
<>
{followInfo == null ? (
t("loading")
) : followInfo.doesFollow ? (
<Button
disabled={isSubmitting}
variant="light"
onClick={() => unfollow(props.for, props.withId)}
>
<FaRegEye />
{t("following")}
</Button>
) : (
<Button
disabled={isSubmitting}
onClick={() => follow(props.for, props.withId)}
>
<FaRegEye />
{t("follow")}
</Button>
)}
</>
);
};
export default FollowButton;
!isCancelled && setFollowInfo(await...) checks the flag and schedules setFollowInfo to execute when data is ready. The flag may change during await.
Try this:
if (!isCancelled) {
const data = await UsersService.amIFollowingUser(
props.withId,
viewer.currentUser?.token
);
!isCancelled && setFollowInfo(data);
}
Also check the documentation for AbortController. It will be better to use it inside UsersService.amIFollowing*

How to test useRef with Jest and react-testing-library?

I'm using create-react-app, Jest and react-testing-library for the configuration of the chatbot project.
I have a functional component that uses useRef hook. When a new message comes useEffect hook is triggered and cause scrolling event by looking a ref's current property.
const ChatBot = () => {
const chatBotMessagesRef = useRef(null)
const chatBotContext = useContext(ChatBotContext)
const { chat, typing } = chatBotContext
useEffect(() => {
if (typeof chatMessagesRef.current.scrollTo !== 'undefined' && chat && chat.length > 0) {
chatBotMessagesRef.current.scrollTo({
top: chatMessagesRef.current.scrollHeight,
behavior: 'smooth'
})
}
// eslint-disable-next-line
}, [chat, typing])
return (
<>
<ChatBotHeader />
<div className='chatbot' ref={chatBotMessagesRef}>
{chat && chat.map((message, index) => {
return <ChatBotBoard answers={message.answers} key={index} currentIndex={index + 1} />
})}
{typing &&
<ServerMessage message='' typing isLiveChat={false} />
}
</div>
</>
)
}
I want to be able to test whether is scrollTo function triggered when a new chat item or typing comes, do you have any ideas? I couldn't find a way to test useRef.
You can move your useEffect out of your component and pass a ref as a parameter to it. Something like
const useScrollTo = (chatMessagesRef, chat) => {
useEffect(() => {
if (typeof chatMessagesRef.current.scrollTo !== 'undefined' && chat && chat.length > 0) {
chatBotMessagesRef.current.scrollTo({
top: chatMessagesRef.current.scrollHeight,
behavior: 'smooth'
})
}
}, [chat])
}
Now in your component
import useScrollTo from '../..'; // whatever is your path
const MyComponent = () => {
const chatBotMessagesRef = useRef(null);
const { chat } = useContext(ChatBotContext);
useScrollTo(chatBotMessagesRef, chat);
// your render..
}
Your useScrollTo test:
import useScrollTo from '../..'; // whatever is your path
import { renderHook } from '#testing-library/react-hooks'
it('should scroll', () => {
const ref = {
current: {
scrollTo: jest.fn()
}
}
const chat = ['message1', 'message2']
renderHook(() => useScrollTo(ref, chat))
expect(ref.current.scrollTo).toHaveBeenCalledTimes(1)
})

useEffect triggers function several times with proper dependencies

i've got Tabs component, it has children Tab components. Upon mount it calculates meta data of Tabs and selected Tab. And then sets styles for tab indicator. For some reason function updateIndicatorState triggers several times in useEffect hook every time active tab changes, and it should trigger only once. Can somebody explain me what I'm doing wrong here? If I remove from deps of 2nd useEffect hook function itself and add a value prop as dep. It triggers correctly only once. But as far as I've read docs of react - I should not cheat useEffect dependency array and there are much better solutions to avoid that.
import React, { useRef, useEffect, useState, useCallback } from 'react';
import PropTypes from 'prop-types';
import { defProperty } from 'helpers';
const Tabs = ({ children, value, orientation, onChange }) => {
console.log(value);
const indicatorRef = useRef(null);
const tabsRef = useRef(null);
const childrenWrapperRef = useRef(null);
const valueToIndex = new Map();
const vertical = orientation === 'vertical';
const start = vertical ? 'top' : 'left';
const size = vertical ? 'height' : 'width';
const [mounted, setMounted] = useState(false);
const [indicatorStyle, setIndicatorStyle] = useState({});
const [transition, setTransition] = useState('none');
const getTabsMeta = useCallback(() => {
console.log('getTabsMeta');
const tabsNode = tabsRef.current;
let tabsMeta;
if (tabsNode) {
const rect = tabsNode.getBoundingClientRect();
tabsMeta = {
clientWidth: tabsNode.clientWidth,
scrollLeft: tabsNode.scrollLeft,
scrollTop: tabsNode.scrollTop,
scrollWidth: tabsNode.scrollWidth,
top: rect.top,
bottom: rect.bottom,
left: rect.left,
right: rect.right,
};
}
let tabMeta;
if (tabsNode && value !== false) {
const wrapperChildren = childrenWrapperRef.current.children;
if (wrapperChildren.length > 0) {
const tab = wrapperChildren[valueToIndex.get(value)];
tabMeta = tab ? tab.getBoundingClientRect() : null;
}
}
return {
tabsMeta,
tabMeta,
};
}, [value, valueToIndex]);
const updateIndicatorState = useCallback(() => {
console.log('updateIndicatorState');
let _newIndicatorStyle;
const { tabsMeta, tabMeta } = getTabsMeta();
let startValue;
if (tabMeta && tabsMeta) {
if (vertical) {
startValue = tabMeta.top - tabsMeta.top + tabsMeta.scrollTop;
} else {
startValue = tabMeta.left - tabsMeta.left;
}
}
const newIndicatorStyle =
((_newIndicatorStyle = {}),
defProperty(_newIndicatorStyle, start, startValue),
defProperty(_newIndicatorStyle, size, tabMeta ? tabMeta[size] : 0),
_newIndicatorStyle);
if (isNaN(indicatorStyle[start]) || isNaN(indicatorStyle[size])) {
setIndicatorStyle(newIndicatorStyle);
} else {
const dStart = Math.abs(indicatorStyle[start] - newIndicatorStyle[start]);
const dSize = Math.abs(indicatorStyle[size] - newIndicatorStyle[size]);
if (dStart >= 1 || dSize >= 1) {
setIndicatorStyle(newIndicatorStyle);
if (transition === 'none') {
setTransition(`${[start]} 0.3s ease-in-out`);
}
}
}
}, [getTabsMeta, indicatorStyle, size, start, transition, vertical]);
useEffect(() => {
const timeout = setTimeout(() => {
setMounted(true);
}, 350);
return () => {
clearTimeout(timeout);
};
}, []);
useEffect(() => {
if (mounted) {
console.log('1st call mounted');
updateIndicatorState();
}
}, [mounted, updateIndicatorState]);
let childIndex = 0;
const childrenItems = React.Children.map(children, child => {
const childValue = child.props.value === undefined ? childIndex : child.props.value;
valueToIndex.set(childValue, childIndex);
const selected = childValue === value;
childIndex += 1;
return React.cloneElement(child, {
selected,
indicator: selected && !mounted,
value: childValue,
onChange,
});
});
const styles = {
[size]: `${indicatorStyle[size]}px`,
[start]: `${indicatorStyle[start]}px`,
transition,
};
console.log(styles);
return (
<>
{value !== 2 ? (
<div className={`tabs tabs--${orientation}`} ref={tabsRef}>
<span className="tab__indicator-wrapper">
<span className="tab__indicator" ref={indicatorRef} style={styles} />
</span>
<div className="tabs__wrapper" ref={childrenWrapperRef}>
{childrenItems}
</div>
</div>
) : null}
</>
);
};
Tabs.defaultProps = {
orientation: 'horizontal',
};
Tabs.propTypes = {
children: PropTypes.node.isRequired,
value: PropTypes.number.isRequired,
orientation: PropTypes.oneOf(['horizontal', 'vertical']),
onChange: PropTypes.func.isRequired,
};
export default Tabs;
useEffect(() => {
if (mounted) {
console.log('1st call mounted');
updateIndicatorState();
}
}, [mounted, updateIndicatorState]);
This effect will trigger whenever the value of mounted or updateIndicatorState changes.
const updateIndicatorState = useCallback(() => {
...
}, [getTabsMeta, indicatorStyle, size, start, transition, vertical]);
The value of updateIndicatorState will change if any of the values in its dep array change, namely getTabsMeta.
const getTabsMeta = useCallback(() => {
...
}, [value, valueToIndex]);
The value of getTabsMeta will change whenever value or valueToIndex changes. From what I'm gathering from your code, value is the value of the selected tab, and valueToIndex is a Map that is re-defined on every single render of this component. So I would expect the value of getTabsMeta to be redefined on every render as well, which will result in the useEffect containing updateIndicatorState to run on every render.

When to use hooks? is worth it that example?

I have write a hook to check if browser is IE, so that I can reutilize the logic instead of write it in each component..
const useIsIE = () => {
const [isIE, setIsIE] = useState(false);
useEffect(() => {
const ua = navigator.userAgent;
const isIe = ua.indexOf("MSIE ") > -1 || ua.indexOf("Trident/") > -1;
setIsIE(isIe);
}, []);
return isIE;
}
export default useIsIE;
Is it worth it to use that hook?
Im not sure if is good idea because that way, Im storing a state and a effect for each hook call (bad performane?) when I can simply use a function like that:
export default () => ua.indexOf("MSIE ") > -1 || ua.indexOf("Trident/") > -1;
What do you think? is worth it use that hook or not?
If not, when should I use hooks and when not?
ty
No. Not worth using the hook.
You'd need to use a hook when you need to tab into React's underlying state or lifecycle mechanisms.
Your browser will probably NEVER change during a session so just creating a simple utility function/module would suffice.
I would recommend to set your browser checks in constants and not functions, your browser will never change.
...
export const isChrome = /Chrome/.test(userAgent) && /Google Inc/.test(navigator.vendor);
export const isIOSChrome = /CriOS/.test(userAgent);
export const isMac = (navigator.platform.toUpperCase().indexOf('MAC') >= 0);
export const isIOS = /iphone|ipad|ipod/.test(userAgent.toLowerCase());
...
This is a simple hook that checks if a element has been scrolled a certain amount of pixels
const useTop = (scrollable) => {
const [show, set] = useState(false);
useEffect(() => {
const scroll = () => {
const { scrollTop } = scrollable;
set(scrollTop >= 50);
};
const throttledScroll = throttle(scroll, 200);
scrollable.addEventListener('scroll', throttledScroll, false);
return () => {
scrollable.removeEventListener('scroll', throttledScroll, false);
};
}, [show]);
return show;
};
Then you can use it in a 'To Top' button to make it visible
...
import { tween } from 'shifty';
import useTop from '../../hooks/useTop';
// scrollRef is your scrollable container ref (getElementById)
const Top = ({ scrollRef }) => {
const t = scrollRef ? useTop(scrollRef) : false;
return (
<div
className={`to-top ${t ? 'show' : ''}`}
onClick={() => {
const { scrollTop } = scrollRef;
tween({
from: { x: scrollTop },
to: { x: 0 },
duration: 800,
easing: 'easeInOutQuart',
step: (state) => {
scrollRef.scrollTop = state.x;
},
});
}}
role="button"
>
<span><ChevronUp size={18} /></span>
</div>
);
};

Resources